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Biomedical subjects

M L Bender

Publications and source records attributed to M L Bender.

At least 73 records · Page 4Linked to original sources
PubMed1969

Alkaline pH dependence of delta-chymotrypsin-catalyzed hydrolysis of specific substrates.

K(m) (app) and k(cat) for the deltachymotrypsin-catalyzed hydrolysis of N-acetyl-L-tryptophan methyl ester and N-furylacryloyl-L-tryptophanamide were measured as a function of pH and ionic strength. The K(m) (app) values do not increase considerably above pH 9 for delta-chymotrypsin, as is the case with alpha-chymotrypsin. The observed kinetic difference between both enzymes at high pH suggests that the reversible inactivation of alpha-chymotrypsin at alkaline pH may involve the participation of tyrosine 146 or alanine 149 since both residues are present as chain termini in alpha-chymotrypsin but not in delta-chymotrypsin.

Catalysis↗
PubMed1969

Esterolytic activity of elastase.

The esters of L-alanine were found to be excellent substrates for elastase. The pH-dependence study using two methyl esters of this substrate showed the participation in the mechanism of an ionizing group with an apparent pK of 6.85 and a decrease of the activity at pH's greater than 10 (that could correspond to an apparent pK of 11.4).

Alanine↗
PubMed1969

The nature of general base-general acid catalysis in serine proteases.

The high reactivity of the serine residue at the active site of serine proteases is often attributed to the formation of a hydrogen bond between this serine and a histidine residue. In the case of the serine protease subtilisin, the catalytic serine residue can be specifically replaced by a cysteine residue and this modified enzyme is called thiol-subtilisin. By studying the D(2)O effect on acyl-enzyme formation with subtilisin and thiol-subtilisin, we present evidence that thiol-subtilisin but not subtilisin may contain a hydrogen bond. Based on the comparison of the catalytic activities of subtilisin and thiol-subtilisin, a rigid active site model for the serine proteases is proposed in which the histidine residue operates in a fixed steric position both as a general base and as a general acid, and this, rather than the formation of a hydrogen bond, accounts for the high nucleophilicity of the serine residue.

Binding Sites↗