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Biomedical subjects

M L Bender

Publications and source records attributed to M L Bender.

At least 55 records · Page 3Linked to original sources
PubMed1973

Influence of Leaving-Group Electronic Effect on alpha-Chymotrypsin: Catalytic Constants of Specific Substrates.

Rate constants and binding constants for the alpha-chymotrypsin-catalyzed hydrolysis of N-acetyltyrosine, tryptophan, and phenylalanine anilides are presented. Both k(cat) and K(m) are independent of electronic effects in the substrate over a range of 9.8 orders of magnitude (as measured by pK of the leaving group). Similarly, K(m) is independent of charge and orientation about the alpha-carbon for various substrates and pseudo-substrates. These results are not consistent with the pretransition state protonation hypothesis; instead, they are discussed in terms of a tetrahedral intermediate that is thermodynamically less stable than the Michaelis complex.

Journal Article↗
PubMed1973

Chymotrypsins.

Explore the source record for details and available documents.

Amino Acids↗
PubMed1971

Inhibition of serine proteases by arylboronic acids.

Arylboronic acids were found to be strong competitive inhibitors of subtilisin and chymotrypsin. The binding constants are strongly pH dependent and give a Hammett-type plot with a slope of -0.885. The pH dependence, the Hammett plot, and nmr model-system studies indicate that inhibition is due to electron-pair donation by the active site histidine to the bound inhibitor.

Bacillus subtilis↗
PubMed1970

Reaction of acetyl-alpha-chymotrypsin and other esters with an ionizable nucleophile, monoisonitrosoacetone.

The rate of deacylation of acetyl-alpha-chymotrypsin is accelerated by the addition of an ionizable nucleophile, monoisonitrosoacetone (pK(a) 8.3) in a linear, first-order fashion at all pH's. The pH dependence of the rate enhancement is a bell-shaped curve with true pK(a)'s at 7.3 and 8.3, corresponding to ionization of an enzyme active site group and of nucleophile, respectively. Extrakinetic evidence and model ester reactions suggest that the most likely mechanism involves neutral imidazole acting as a general base toward protonated monoisonitrosoacetone, rather than protonated imidazole acting as a general acid to assist the attack of monoisonitrosoacetone anion.

Chemical Phenomena↗