Reference

Mechanism of action of adenosylcobalamin: glycerol and other substrate analogs as substrates and inactivators for propanediol dehydratase - kinetics, stereospecificity, and mechanism

Mechanism of action of adenosylcobalamin: glycerol and other substrate analogs as substrates and inactivators for propanediol dehydratase - kinetics, stereospecificity, and mechanism. Bachovchin, William W.; Eagar, Robert G., Jr.; Moore, Kevin W. 62502-72-1 and 4254-15-3 are also occured in this study.; Richards, John H. (Church Lab. Chem. Biol., California Inst. Technol., Pasadena, Calif., USA). Biochemistry, 16(6), 1082-92 (English) 1977. CODEN: BICHAW. DOCUMENT TYPE: Journal CA Section: 7 (Enzymes) A no. of vicinal diols reacted with propanediol dehydratase (I), resulting in the conversion of I-bound adenosylcobalamin to cob(II)alamin and formation of aldehyde or ketone from substrate. Moreover, all are capable of effecting the irreversible inactivation of I. Glycerol, a very good substrate for I as well as a potent inactivator, atypically, did not induce cob(II)alamin formation. With glycerol, the inactivation process was accompanied by conversion of I-bound adenosylcobalamin to an alkyl or thiol cobalamin, probably by substitution of an amino acid side chain near the active site for the 5'-deoxy-5'-adenosyl ligand on the cobalamin. The inactivation reaction with glycerol exhibits a 2H isotope effect of 14, strongly implicating H transfer as important in the inactivation. I distinguishes between R and S binding conformations, the I-(R)-glycerol complex being predominately responsible for the product-forming reaction, whereas the I-(S)-glycerol complex results primarily in the inactivation reaction. Mechanistic implications are discussed. A method for removing I-bound hydroxycobalamin that is nondestructive to I and a technique for measuring the binding consts. of (R)- and (S)-1,2-propanediols are presented. .

Mechanistic Studies on Full Length and the Catalytic Domain of the Tandem SH2 Domain-Containing Protein Tyrosine Phosphatase: Analysis of Phosphoenzyme Levels and Vmax Stimulatory Effects of Glycerol and of a Phosphotyrosyl Peptide Ligand

Mechanistic Studies on Full Length and the Catalytic Domain of the Tandem SH2 Domain-Containing Protein Tyrosine Phosphatase: Analysis of Phosphoenzyme Levels and Vmax Stimulatory Effects of Glycerol and of a Phosphotyrosyl Peptide Ligand.Some chemicals with cas registry numbers like 67-63-0 and 4254-15-3 are also used. Wang, Jun; Walsh, Christopher T. (Department of Biological Chemistry Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA). Biochemistry, 36(10), 2993-2999 (English) 1997 American Chemical Society. CODEN: BICHAW. ISSN: 0006-2960. DOCUMENT TYPE: Journal CA Section: 7 (Enzymes) SHP-1, a protein tyrosine phosphatase contg. two tandem SH2 domains, is autoinhibited at rest by its N-terminal SH2 (N-SH2) domain. Relief from autoinhibition and a subsequent 10-60-fold increase in Vmax have been obsd. upon N-SH2 domain engagement by a specific phosphotyrosyl ligand or upon deletion of the N-SH2 domain to yield the catalytic PTPase domain. In this study, we obsd. that glycerol and propane-1,2-diols, at concns. of 4-6 M, accelerated the kcat of the full length enzyme by 47-fold and of the PTPase domain by 8-fold. Glycerol also increases the rate of proteolytic cleavage between the SH2 and catalytic PTPase domains. In stopped-flow studies using p-nitrophenyl phosphate (pNPP) as a substrate, a burst of p-nitrophenolate in the full length enzyme was not obsd.; however, a 50-70% stoichiometric burst was obsd. with the PTPase domain. Rapid quench studies using [32P]pNPP as a substrate showed a very low level of covalent [32P]phosphocysteinyl enzyme intermediate accumulation: 0.06% in the full length enzyme and 1% in the PTP domain. Stimulation by glycerol reduced the accumulating levels of phosphocysteinyl enzyme in both cases of full length SHP-1 and the PTPase domain; however, glycerol is not acting as a cosubstrate since no glycerophosphate product was detectable. It is likely that, for full length SHP-1, with pNPP as a model substrate, enzyme-substrate complex (ES) accumulates in its basal autoinhibited state, whereas enzyme-product complex (EPi) accumulates in its pY ligand-bound activated state. Glycerol probably relaxes the compact structure of SHP-1 and the PTP domain, thereby accelerating the catalytic rates in both cases by increasing forward reaction rates of ES and EPi. .