29739-71-7Relevant academic research and scientific papers
Solid-state proton/sodium buffers: Chemical pH stats for biocatalysts in organic solvents
Partridge, Johann,Halling, Peter J.,Moore, Barry D.
, p. 465 - 471 (2007/10/03)
The useful application of enzymes in organic synthesis requires reliable and straightforward methods for maximising efficiency and selectivity. Here we describe how to control the protonation state of enzymes using a new class of solid-state buffers, applied for the first time in polar organic solvents. Remarkably these insoluble buffers are able to rapidly exchange H+ and Na+ ions with both the protein and reaction mixture as demonstrated here using propanol rinsed enzyme preparations (PREPs) of subtilisin Carlsberg and chymotrypsin. The buffers tested were generally mixtures of a zwitterionic biological buffer and its Na+ salt with each buffer pair setting a characteristic fixed ratio of H+ activity to Na+ activity (aH+/aNa+) within the system. Dependent upon the solid buffer pair selected a wide range of different enzymatic activities could be observed. The variation in rate showed a fairly good but not exact correlation with the aqueous pKa of the buffers, indicating that crystal lattice energies have less affect on acid-base strength than might be expected. The solid-state buffers were able to prevent detrimental changes to enzyme activity caused by the presence or build up of acids or bases in the organic reaction mixture (often undetected). They could also be used advantageously to tune the enzyme protonation state in solvent if a previous aqueous preparation step needs to be carried out at a pH not optimal for catalysis. Such buffering systems are expected to find wide-spread use as 'chemical pH stats' for reactions in non-aqueous media.
PEPTIDE SYNTHESIS CATALYZED BY NATIVE PROTEINASE K IN WATER-MISCIBLE ORGANIC SOLVENTS WITH LOW WATER CONTENT
Cerovsky, Vaclav,Martinek, Karel
, p. 2027 - 2041 (2007/10/02)
Rection of Ac-Tyr-OEt with HBr.Gly-NH2, catalysed by free proteinase K in various water-miscible organic solvents in the presence of triethylamine and 5 mol percent of water, was studied.Some aliphatic alcohols and acetonitrile proved to be suitable solvents.The effect of water content (2 percent - 20 percent) on the synthesis of Ac-Tyr-Gly-NH2 was studied using acetonitrile as solvent.Lowering of the water content to 5 percent or 2 percent led to almost 100 percent yield of the desired dipeptide; higher water content accelerated the reaction reducing at the same time the yield of Ac-Tyr-Gly-NH2 due to the concurrent hydrolysis of the ester Ac-Tyr-OEt.No reaction was observed in the absence of base (triethylamine), wereas an excess of base only retarded the reaction.The enzyme is capable of catalyzing the peptide bond synthesis with N-acylamino acids or N-acyl peptides as acylating components, which may contain all types of L-amino acid residues (except Pro) in the P1 position.However, the peptide bond synthesis depends strongly on the amino component composition, particularly on the amino acid residue in the P'1 position.Only amides of glycine and of hydrophillic amino acids were acylated with Ac-Tyr-OEt; amides of hydrophobic amino acids enter the reaction only reluctantly or not at al.The presence of Leu or Phe in position P'2 and Leu in position P'3 has not so negative effect on acylation of the amino component as has in presence in the P'1 position.The choice of protecting groups for the α-carboxyl of the amino component is restricted only to amide and in some cases its undesired enzymatic removal was observed.Unprotected peptides seem to be suitable amino components.
