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Biomedical subjects

C J Gray

Publications and source records attributed to C J Gray.

33 records · Page 2Linked to original sources
PubMed1977

Properties of enzymes immobilized by the diazotized m-diaminobenzene method.

Some properties of a number of enzymes immobilized by the diazotized m-diaminobenzene (dDAB) method are described. The pH-activity profiles of beta-D-glucosidase, glucoamylase, peroxidase, uricase, and D-glucose oxidase were virtually unchanged on immobilization while those of catalase and dextranase were significantly altered. beta-D-Glucosidase, glucoamylase, and glucose oxidase were found to be more susceptible to denaturation on lyophilization when immobilized than in the native state; however, sorbitol had a marked protective effect in every case examined. Sorbitol was also found to exert a stabilizing effect when lyophilized immobilized preparations were stored. Immobilization marginally improved the stabilities of a number of enzymes to heating at 60 degrees at pH 8.0. The usefulness for continuous reaction of a column of glucoamylase attached to celite was established. The reuse of the solid supports was demonstrated.

Aniline Compounds↗
PubMed1976

Tryptophanyl and carboxylic acid residues in the active centre of glucoamylase I from Aspergillus niger.

The pH-dependence of the photo-oxidation of L-tryptophan, in the presence of Rose Bengal and Methylene Blue, has been investigated. True, initial rate constants were determined in order to circumvent errors due to secondary processes. Photo-oxidation of glycoamylase I from A. niger in the presence of Methylene Blue or Rose Bengal resulted in a pH-dependent loss of enzymic activity, which was analogous to the destruction of free L-tryptophan during photo-oxidation. The loss of enzymic activity was closely associated with the destruction of tryptophan residues in the enzyme. Significant protection of both enzymic activity and tryptophanyl residues in the enzyme molecule was achieved by performing the photo-oxidation in the presence of maltose, which is a substrate for the enzyme. The tryptophanyl residues of glucoamylase I, which had been inactivated by reaction of its carboxylic acid residues with glycine methyl ester in the presence of a water-soluble carbodi-imide, were also substantially protected by maltose. It is concluded that the active centre of glucoamylase I is a cleft lined with tryptophanyl residues that participate in the binding of the substrate. One or more carboxylic acid residues are involved in bond cleavage.

Aspergillus↗
PubMed1974

The reaction of an alpha-aza-amino acid derivative with chymotrypsin and its use as a ligand for covalent affinity purification.

1. Chymotrypsin is inactivated by N-acetyl-alpha-azaphenylalanine phenyl ester (phenyl N(2)-acetyl-N(1)-benzylcarbazate) in a stoicheiometric reaction. 2. The inactivation is reversible spontaneously (first-order rate constant is 1.2x10(-4)s(-1)) and accelerated by the presence of hydroxylamine. 3. Polymers based on polyacrylamide and carrying ligands containing the alpha-azaphenylalanine phenyl ester group were prepared. 4. Chymotrypsin reacts with these polymers and is removed by them from solution. Trypsin reacts less rapidly. 5. Chymotrypsin is slowly released from the polymer spontaneously and more rapidly on treatment with hydroxylamine. 6. The reaction of trypsin can be inhibited by competitive inhibitors. 7. Chymotrypsin was separated from trypsin by the selective bonding of chymotrypsin on to and its subsequent liberation from one of the polymers described.

Acrylamides↗