Hydroxamic Acid-Piperidine Conjugate is an Activated Catalyst for Lysine Acetylation under Physiological Conditions

Article abstract of DOI:10.1002/asia.201901737

Lysine acylation of proteins is an essential chemical reaction for posttranslational modification and as a means of protein modification in various applications. N,N-Dimethyl-4-aminopyridine (DMAP) derivatives are widely-used catalysts for lysine acylatio

Full text of DOI:10.1002/asia.201901737

CHEMISTRY
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Accepted Article
Title: Hydroxamic Acid-Piperidine Conjugate is an Activated Catalyst
for Lysine Acetylation under Physiological Conditions
Authors: Shinsuke Mizumoto, Siqi Xi, Yusuke Fujiwara, Shigehiro A
Kawashima, Kenzo Yamatsugu, and Motomu Kanai
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10.1002/asia.201901737
Chemistry - An Asian Journal
Hydroxamic Acid-Piperidine Conjugate is an Activated
Catalyst for Lysine Acetylation under Physiological
Conditions
Shinsuke Mizumoto (水本真介)1, Siqi Xi (席思奇)1, Yusuke Fujiwara (藤原侑亮)1,
Shigehiro A. Kawashima (川島茂裕)1, Kenzo Yamatsugu (山次健三)1,*, & Motomu
Kanai (金井求)1,*
1Graduate School of Pharmaceutical Sciences, The University of Tokyo, 7-3-1 Hongo,
Bunkyo-ku, Tokyo 113-0033, Japan
*Corresponding Authors:
Motomu Kanai (Email: kanai@mol.f.u-tokyo.ac.jp)
Kenzo Yamatsugu (Email: yamatsugu@mol.f.u-tokyo.ac.jp)
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Abstract
Lysine acylation of proteins is an essential chemical reaction for posttranslational
modification and as a means of protein modification in various applications.
N,N-Dimethyl-4-aminopyridine (DMAP) derivatives are widely-used catalysts for
lysine acylation of proteins; however, the DMAP moiety mostly exists in a protonated,
and thus deactivated, form under physiological conditions due to its basicity. An
alternative catalytic motif furnishing higher acylation activity would further broaden the
possible applications of chemical lysine acylation. We herein report that the hydroxamic
acid-piperidine conjugate Ph-HXA is a more active catalytic motif for lysine acetylation
than DMAP under physiological conditions. In contrast to DMAP, the hydroxamic acid
moiety is mostly deprotonated under aqueous neutral pH, resulting in a higher
concentration of the activated form. The Ph-HXA catalyst is also more tolerant of
deactivation by a high concentration of glutathione than DMAP. Therefore, Ph-HXA
might be a suitable catalytic motif for target protein-selective and site-selective
acetylation in cells.
Keywords
acylation, catalyst, hydroxamic acid, lysine acetylation, protein modifications
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Introduction
Chemical modifications of proteins are pivotal both in life and physical
science.[1] Among the proteinogenic amino acids, lysine is nucleophilic and highly
solvent-exposed,[2] thus rendering it one of the most accessible amino acid residues for
protein modifications. For example, acylation and methylation of histone protein lysine
residues in cellular chromatin are intimately related to the control of gene expression
and fundamental to epigenetics.[3] Attachment of molecular probes and cytotoxic
payloads to protein lysine residues is a platform technology for investigating the
functions/distributions of proteins and for synthesizing antibody-drug conjugates,
respectively.[1] A chemical method enabling modification of lysine residues in a protein
of interest is, therefore, critical for elucidating the biological functions of endogenous
post-translational modifications (e.g., histone epigenetics) and also for manipulating or
improving the functions of native proteins (e.g., antibody-drug conjugates).
A ligand-directed catalysis using a catalyst molecule comprising a catalytic
motif and a protein ligand, combined with an acyl donor reagent, has allowed for target
protein-selective and site-selective lysine acylation (Scheme 1a).[4] The ligand moiety of
the catalyst binds to a target protein, wherein the catalytic motif activates an acyl donor
and generates a reactive intermediate proximal to the specific lysine residue determined
by
the
protein
ligand,
resulting
in
selective
lysine
acylation.
N,N-Dimethyl-4-aminopyridine (DMAP) is the most frequently-used catalytic motif in
ligand-directed lysine acylation (Scheme 1a).[5] The ligand-directed DMAP (1)
derivatives achieved selective lysine acylation in test tubes,[5e] on the cellular surface,[5b,
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5c, 5g]
and in living cells.[6] This method was successfully used for bioimaging of
proteins[5c, 5g, 7] and analysis of protein-protein interactions.[5b] Nucleosome-binding
ligand-directed DMAP derivatives, such as DSH (2, Scheme 1a), promoted synthetic
histone acylation; this elucidated the function of histone acylation and the enzymes that
regulate it,[5a, 5d, 8] as well as allowed the proposal of a new potential therapeutic strategy
utilizing gene expression control by synthetic histone acylation.[9]
Considering the utility of ligand-directed lysine acylation, more reactive
catalysts enabling faster reactions at lower quantities than DMAP would further broaden
potential applications of this approach. In organic solvents, DMAP derivatives bearing
more electron-rich pyridine rings are more reactive catalysts due to enhanced
nucleophilicity.[10] Under physiological conditions, however, the more electron-rich
DMAP derivatives are more protonated (pKa of the protonated DMAP: 9.2). The
protonated DMAP is an inactive nucleophilic catalyst (Scheme 1b).[11] A different
approach from increasing electron density of the pyridine ring of the DMAP derivatives
is, thus, necessary to obtain more reactive acylation catalysts.[7] Herein, we report that
hydroxamic acid-piperidine conjugate Ph-HXA is a more reactive catalyst for lysine
acetylation of proteins under physiological conditions than DMAP (Scheme 1c). The
hydroxamic acid moiety of the catalyst was mostly deprotonated under physiological
conditions, producing an activated catalytic center unlike the protonated, and thus
deactivated, catalytic center observed in the DMAP derivatives.
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Scheme 1. Molecular design. (a) Ligand-directed catalysis. Representative catalytic
motifs are shown. (b) DMAP derivatives are protonated under physiological conditions,
affording an inactive form. (c) This study: the hydroxamic acid is deprotonated under
physiological conditions, affording an activated form.
Results
Optimization of the catalytic motif
To find a more reactive catalytic motif than DMAP, we conducted a kinetic
analysis of lysine acetylation using a peptide containing a catalyst candidate and a
lysine residue in one molecule as a simplified model of ligand-directed acetylation of a
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protein (Figure 1a).[11] We focused on a hydroxamic acid as a nucleophilic catalyst motif,
based on previous reports describing hydroxamic acid derivatives as good catalysts or
additives for acylation reactions of amines in organic solvents[12] and hydrolysis
reactions of activated phenyl esters under aqueous neutral conditions.[13] In the ester
hydrolysis reactions, a hydroxamic acid conjugated with a basic functional group, such
as a tertiary amino group, was more reactive than those lacking basic functional groups,
indicating the formation of a zwitterion species (e.g., 18 in Scheme 2) and a
corresponding decrease in pKa value of the hydroxamic acid moiety. We therefore
designed and synthesized several types of hydroxamic acid compounds 4–7 (Figure 1a).
The catalyst-conjugated peptides were prepared by standard solid-phase peptide
synthesis (see Supporting Information). The peptides (0.5 mM) were dissolved in
Tris-HCl buffer (250 mM, pH 7.5) and were treated with an acetyl donor, PAc-gly (9, 5
mM, a water soluble phenylacetate derivative, Figure 1b). The acetyl group in PAc-gly
is first activated by the catalytic motif at the N-terminus of the peptide, followed by an
intramolecular transfer of the activated acetyl group to the lysine residue to complete
the reaction. The progress of the acetyl-transfer reaction was monitored by high
performance liquid chromatography (HPLC, Figure 1c). When using DMAP as a
catalytic motif, acetylation of the lysine residue reached 57% yield after 240 minutes (3,
Figure 1c). The initial rate of the acetyl-transfer reaction for peptide 4 containing a
hydroxamic acid catalytic motif was 1.7-fold faster than that of 3, reaching 66% yield
after 240 minutes. Peptide 5 was less reactive than 4, and showed similar or less
acetyl-transfer activity compared to 3 containing DMAP. These results suggest that the
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acidity of the hydroxamic acid has profound effects on its acetyl-transfer activity. We
therefore synthesized peptide 6 containing the N-phenyl hydroxamic acid catalytic
moiety Ph-HXA, whose hydroxamic acid moiety would have higher acidity than 5 due
to conjugation of a phenyl group with the nitrogen atom. The acetyl-transfer reaction of
6 proceeded more efficiently than other peptides, and its initial rate was 3.9-fold faster
than that of 3. Peptide 7, which has a cyclohexyl group instead of the piperidine group
of Ph-HXA (6), showed significantly reduced acetyl-transfer activity, clearly showing
the importance of the basic functionality in the catalysis (Figure 1c). Peptide 8
contained a benzoyl group instead of a catalytic motif. This peptide exhibited very low
reactivity (Figure 1c), indicating that catalyst-independent background acetylation is
negligible compared to the catalyst-promoted reaction using acetyl-donor 9.
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a
O
O
O
Me
N
N
N
N
N
N
OH
OH
O
O
DMAP (3)
4
5
O
O
O
O
Peptide
O
N
N
N
(Peptide = [Catalytic motif]-linker-Ala-Lys-Phe-Arg-NH2)
OH
OH
Ph-HXA (6)
7
8
b
N
N
N
O
O
O
Cat
Cat
HN
NH2
NH
HN
NH2
NH
HN
HN
O
HN
NH2
O
HO
PAc-gly (
O
O
O
9
)
O
O
O
H
H
H
H
N
N
NH2
N
N
NH2
Tris-HCl (pH 7.5), 37 °C
w/ or w/o GSH
O
N
N
O
N
N
H
H
H
H
O
O
O
O
O
O
GSH: Glutathione
HS
O
O
O
H
N
HO
N
OH
H
NH2
O
c
d
3
6
100
80
60
40
20
0
3
100
80
60
40
20
0
cat
krel
4
5
6
7
8
3
4
5
6
7
8
1.00
1.71
0.71
3.89
0.99
0.02
cat
3
krel
1.00
6
60.11
0
60
120
Time (min.)
180
240
0
120
240
Time (min.)
360
480
Figure 1. Optimization of the catalytic motif. (a) Investigated candidates for the
catalytic motif. (b) A general scheme of the lysine acetylation reaction. (c) Acetylation
profiles using peptides with different catalytic motifs. Relative initial rate to
DMAP-containing peptide 3 is shown in the Table. (d) Acetylation profiles using
peptides with DMAP (3) or Ph-HXA (6) in the presence of 5 mM glutathione. Relative
initial rate to DMAP-containing peptide 3 is shown in the Table. Error bars denote range
(n = 2).
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Glutathione (GSH) is a tripeptide, which serves as a major intracellular
reductant/nucleophile (Figure 1b). The concentration of GSH in cells varies from 0.5
mM to 10 mM depending on the subcellular location.[14] The nucleophilicity of the
cysteine in GSH and its abundance in cells make it a major inhibitor of synthetic
nucleophilic catalysis in cells.[5a] Because the active species generated by the
hydroxamic acid is different from that generated by DMAP (i.e., acetyl pyridinium ion),
we anticipated that the tolerance of the active species toward GSH may be different and
result in different lysine acetylation activity in the presence of GSH. Therefore, we
conducted the acetyl transfer reaction using DMAP-containing peptide 3 and
Ph-HXA-containing peptide 6 in the presence of 5 mM GSH (Figure 1d). While lysine
acetylation by 3 was significantly inhibited by the presence of GSH, the reaction by 6
was less affected and demonstrated an acetyl transfer rate 60-fold faster than 3.
Application of Ph-HXA catalytic motif to lysine acetylation of a protein
Next, we applied the Ph-HXA catalytic motif to ligand-directed lysine
acetylation of a protein (Figure 2). We chose E.coli dihydrofolate reductase (eDHFR) as
a model protein substrate because there is a well-established small molecule ligand,
trimethoprim (TMP), that selectively binds to this protein. Two catalysts,
Ph-HXA–TMP (10) and DMAP–TMP (11), were synthesized as shown in the
Supporting Information (Figure 2a). The catalysts (50 µM) were incubated with
eDHFR-EGFP (5 µM) in HEPES buffer (50 mM, pH 7.9) with PAc-gly (5 mM) in the
presence of HEK293T cell lysate and 5 mM of GSH, and the acetylation yield of lysine
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32 (K32) proximal to the TMP-binding site was determined by liquid
chromatography-tandem mass spectrometry (LC–MS/MS) analysis (see Experimental
section and Supporting Information).[6] Consistent with the investigations using peptides
(Figure 1), Ph-HXA–TMP 10 promoted lysine acetylation more strongly than
DMAP–TMP 11 (Figure 2b), demonstrating the utility of the Ph-HXA catalyst in the
protein acetylation reaction.
Figure 2. Ligand-directed catalytic acetylation of eDHFR-EGFP. (a) Structures of
catalysts. (b) Reaction profiles of K32 catalytic acetylation of eDHFR-EGFP. Error bars
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denote range (n = 2).
Mechanistic investigation
Next, we examined the mechanism of the acetyl-transfer reaction with the
hydroxamic acid-piperidine conjugate catalyst (Figure 3). Firstly, we carried out proton
nuclear magnetic resonance (1H NMR) experiments to determine the pKa value of the
active site hydroxamic acid moiety in the Ph-HXA catalyst. We measured the chemical
shift of proton Ha in Ph-HXA-NHMe 12 under various pH conditions. As a result, a
plot containing two inflection points was obtained (Figure 3a). This is likely due to the
existence of two acid/base moieties in 12, the hydroxamic acid and the piperidine
moieties. A well-fitted theoretical curve (the broken line in Figure 3b) was obtained
based on the equation shown in Figure 3b, where the hydroxamic acid and piperidine
moieties change their protonation states independently. For clarity, the theoretical
curves derived from the terms in red and in blue in the equation were shown in Figure
3b. Considering the basicity of the piperidine moiety, the curve shown in blue is
attributed to the piperidine moiety, and that in red is attributed to the hydroxamic acid
moiety. According to the equation, the pKa value of the hydroxamic acid moiety in
Ph-HXA was determined to be 6.5, and approximately 90% of Ph-HXA is present in a
1
deprotonated form under pH 7.5 conditions. On the other hand, the same H NMR
experiments were conducted with DMAP-NHMe S20, and the pKa of the protonated
DMAP moiety was determined to be 8.6 under pH 7.5 conditions, which indicated that
only 8% was deprotonated under the same conditions. These results support the
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hypothesis that the Ph-HXA catalyst is activated by deprotonation under physiological
conditions to generate an active nucleophilic species, giving it a higher acetyl-transfer
activity than the DMAP catalyst (Figures 1 and 2).
Figure 3. Mechanistic investigations. (a) Chemical shift of proton Ha in
Ph-HXA-NHMe 12 was plotted under various pH conditions. (b) An equation to obtain
the fitting curve. The curve in red was described by the term in red in the equation. The
curve in blue was described by the term in blue in the equation. The dependency of the
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degree of protonation form in 12 on pH was simulated by the summation of the two
curves (broken line). (c) Step-wise analysis of the reaction pathway. Cyclohexane-type
hydroxamic acid connected with a Boc-protected lysine (13) was treated with PAc-gly
to form its O-acetylated product (14). The isolated 14 was treated with TFA to remove
its Boc-group to generate 15, which transfers its O-acetyl group to the lysine residue
upon being dissolved in aqueous neutral buffer, providing an N-acetylated product (16).
Next, we attempted identification of the active intermediates of this acetyl
transfer reaction. Initially, we attempted to detect an O-acetyl intermediate derived from
Ph-HXA by reacting the Ph-HXA-containing peptide (6-LysAc), in which the lysine
residue was acetylated in advance, with PAc-gly (Figure S1a). The O-acetyl
intermediate was not detected by HPLC analysis, however, possibly due to its high
reactivity. We therefore conducted the same experiment using the less reactive
hydroxamic acid-cyclohexane-conjugated peptide (7-LysAc, Figures 3c and S1b). As a
result, a new peak was observed by HPLC analysis, which was identified as an O-acetyl
intermediate from LCMS analysis. This result indicates that the hydroxamic acid
moiety generates an O-acetyl intermediate by reacting with the acetyl donor. We then
investigated the reactivity of the O-acetyl intermediate. We prepared a hydroxamic
acid-cyclohexane-conjugated peptide with a tert-butoxycarbonyl (Boc)-protected lysine
residue (13), and monitored its reactivity with PAc-gly by HPLC analysis (Figures 3c
and S2). When treated with PAc-gly, 13 generated its O-acetyl product 14, and it was
isolated with HPLC. Isolated 14 was then treated with trifluoroacetic acid (TFA) to
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remove the Boc group, generating a non-protected lysine as its TFA salt 15. Upon
dissolving this intermediate in aqueous neutral buffer (Tris-HCl, pH 7.5), the acetyl
transfer reaction from the O-acetylated hydroxamate to the lysine residue occurred,
affording N-acetylated product 16 in 75% yield. These results suggest that the Ph-HXA
catalyst activates the acetyl group of PAc-gly through its deprotonated hydroxamic acid
moiety and transfers the acetyl group to a proximal substrate lysine residue.
Postulated mechanism of lysine acetylation by Ph-HXA catalyst
A postulated reaction mechanism of lysine acetylation by the Ph-HXA
catalyst is shown in Scheme 2. The hydroxamic acid moiety in Ph-HXA 17 mostly
exists in its deprotonated active form 18 under physiological conditions, and it activates
the acetyl group in the acetyl donor, PAc-gly, to generate activated O-acetyl
intermediate 19. When a lysine group is proximal to 19, it transfers its activated acetyl
group to the -amino group of the lysine, and regenerates the Ph-HXA catalyst.
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O
HN
Lys
O
O
N
N
OH
NH2
Lys
O
O
O
O
N
N
O
N+
H
N
O-
O
R
R
O
O
Ac-donor
HO
Scheme 2. A postulated mechanism of lysine acetylation by Ph-HXA.
Discussion
In this study, we showed that a hydroxamic acid-piperidine conjugate
Ph-HXA 6 is an active nucleophilic catalyst for lysine acetylation under physiological
conditions. This is the first example of using a hydroxamic acid for protein lysine
acylation under physiological conditions. The optimized catalyst 6 has 4-fold higher
activity than the cyclohexane cognate 7 (Figure 1c). The effect of the piperidine moiety
in enhancing the catalyst activity is intriguing. One possible role of the piperidine
moiety is decreasing the pKa value of the hydroxamic acid moiety by forming a stable
zwitterion species. The generated hydroxamate works as an active nucleophilic species.
Another possibility is that the piperidine moiety might activate the -amino group of the
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substrate lysine residue through forming a hydrogen bond to enhance proximity effect
or working as a base to facilitate deprotonation of the protonated lysine -amino
group.[13b] Introduction of basic functional groups other than the piperidine moiety, and
elucidation of their roles, would aid in the development of new, and potentially more
active, nucleophilic hydroxamic acid catalysts.
Another noteworthy characteristic of the hydroxamic acid catalyst is its higher
tolerance of deactivation by GSH compared to DMAP (Figures 1d and 2b). This feature
is important for application to in-cell lysine acetylation reactions,[5f, 6] because GSH is
abundant (0.5~10 mM) in cells and inhibits synthetic acetylation by reacting with the
reactive intermediates generated by the catalysts. One reason for the lower susceptibility
to GSH may be that the activated acetyl intermediate generated from the hydroxamic
acid catalyst (i.e., acetyl hydroxamate) is thermodynamically more stable than the
corresponding activated acetyl pyridinium ion generated from DMAP. Another
possibility is that the electronically-neutral acetyl hydroxamate is kinetically less
reactive to anionic GSH than the cationic acetyl pyridinium ion intermediate.
We previously reported that DSH (2, Scheme 1a) activates less reactive
aliphatic thioester acyl donors, such as acyl-CoA, enabling histone acylation in test
tubes[5a] and protein acylation in living cells.[6] This catalysis exploits a dynamic
thiol-thioester exchange reaction between the thiol group in DSH and thioester acyl
donors, followed by nucleophilic activation of the intercepted acetyl group with the
DMAP skeleton, to enable site-selective protein acylation. Kinetic analyses of the
DSH-mediated lysine acetylation revealed that the thiol-thioester exchange proceeded
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smoothly and the subsequent acetyl transfer from the acetylated catalyst to a substrate
lysine residue mediated by the nucleophilic catalyst moiety was rate-determining.[11]
Combining this previous knowledge with the present study, introduction of a thiol group
into the hydroxamic acid-piperidine conjugates may provide a more potent catalyst
capable of activating less-reactive thioester acyl donors. Investigations in that direction
are now in progress.
Conclusion
We showed that, compared to DMAP, the hydroxamic acid-piperidine
conjugate catalyst Ph-HXA is a superior nucleophilic catalyst for lysine acetylation
reactions under physiological conditions. Several mechanistic investigations indicated
that the hydroxamic acid moiety is activated by deprotonation under physiological
conditions to work as an active nucleophilic catalyst. Because a ligand-directed
catalysis approach is useful for protein modifications for various biochemical purposes,
the design and identification of the hydroxamic acid-piperidine conjugate catalysts in
this study would have a large impact to further broaden its applications.
Experimental Section
Lysine acetylation using catalyst-peptide conjugates
A peptide (0.5 mM) containing a catalyst moiety and a lysine residue was incubated
with PAc-gly (5 mM) in Tris-HCl buffer (250 mM, pH 7.5) at 37 °C for the indicated
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time. At each time point, a dithiothreitol aqueous solution (DTT, final 50 mM) was
added, and the mixture was incubated for 10 min to convert all the acetyl hydroxamate
intermediates on the peptides back to hydroxamic acids. The reaction was then treated
with 0.15% TFA aqueous solution (final TFA concentration is 0.14%) and analyzed with
HPLC (uv: 230 nm). The conversion yields were calculated by dividing the peak area of
the acetylated product by the sums of those of the starting peptide and the acetylated
product.
eDHFR-EGFP acetylation in the presence of HEK293T cell lysate
TMP-conjugated catalyst (50 µM) and PAc-gly (1 mM) were added to HEPES buffer
(50 mM HEPES-KOH (pH 7.9), 150 mM NaCl, 0.01% Triton-X), before eDHFR-GFP
(5 µM) was added to the solution. The mixture was incubated at 37 °C. After the
indicated time, 4 μL of trichloroacetic acid was added to 20 μL of the reaction mixture,
and the mixture was incubated at 4 °C for 16 h. The mixture was centrifuged (15,000
rpm, 10 min), and the supernatant was removed. The residue was suspended in 300 µL
of acetone, centrifuged (15,000 rpm, 10 min), and the supernatant was removed.
Acetone precipitation was repeated, and the remaining solvent was evaporated using a
Speed-Vac evaporator. The residue was dissolved in 10 µL of Milli-Q water, and 10 µL
of 200 mM NH4HCO3 aq., 20 μL of MeOH/propionic anhydride (3/1), and 14 μL of
28% ammonia solution were added. After 30 min incubation at r.t., the solvents were
removed by a Speed-Vac evaporator at 80 °C. The residue was dissolved in 50 µL of 50
mM NH4HCO3 aq.. To the sample, 1 µL of 1% protease MAX, 1 µg trypsin gold, and 1
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µg Glu-C were added, and the mixture was incubated at 37 °C for 17 h. To the mixture,
25 μL of 5% formic acid aq. was added, and the solvent was removed using a
Speed-Vac evaporator at 80 °C. The dried sample was dissolved in 0.1% formic acid
and centrifuged (15,000 rpm, 10 min). The supernatant was used for LC–MS/MS
analysis. For the details of the LC– MS/MS analysis, see Supporting Information.
Acknowledgements
We appreciate Ryan M. Newlon for providing useful comments on the
manuscript. This work was supported by a Grant-in-Aid for Scientific Research on
Innovative Areas Chemistry for Multimolecular Crowding Biosystems Grant no.
18H04536 (K.Y.), Grant-in-Aid for Scientific Research (A) Grant no. 17H01522 (M.K.),
Fund for the Promotion of Joint International Research (Fostering Joint International
Research (B) Grant no. 19KK0179 (M.K., K.Y., and S.A.K.), and the ‘Epigenome
Manipulation Project’ of the All-RIKEN Projects supported by RIKEN.
Conflicts of Interest
The authors declare no conflict of interest.
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10.1002/asia.201901737
Chemistry - An Asian Journal
This article is protected by copyright. All rights reserved.

10.1002/asia.201901737
Chemistry - An Asian Journal
A proposed Table of Contents Graphic
FULL PAPER
A hydroxamic acid-piperidine
conjugate is a superior lysine
acetylation catalyst for protein
modifications to
Shinsuke Mizumoto, Siqi Xi, Yusuke
Fujiwara, Shigehiro A. Kawashima,
Kenzo Yamatsugu*, & Motomu Kanai*
Page No. – Page No.
N,N-dimethyl-4-aminopyridine
(DMAP). It is activated through
deprotonation under physiological
conditions, and is less susceptible to
inactivation by glutathione.
Hydroxamic Acid-Piperidine
Conjugate is an Activated Catalyst
for Lysine Acetylation under
Physiological Conditions
Under physiological conditions
Less affected by glutathione
This article is protected by copyright. All rights reserved.