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.

Medienart:

Artikel

Erscheinungsjahr:

1976

Erschienen:

1976

Enthalten in:

Zur Gesamtaufnahme - volume:49

Enthalten in:

Carbohydrate research - 49(1976) vom: 17. Juli, Seite 361-70

Sprache:

Englisch

Beteiligte Personen:

Jolley, M E [VerfasserIn]
Gray, C J [VerfasserIn]

Themen:

1ZPG1ELY14
8DUH1N11BX
Carboxylic Acids
EC 3.2.1.-
Glucosidases
Journal Article
Methylene Blue
Rose Bengal
T42P99266K
Tryptophan

Anmerkungen:

Date Completed 01.12.1976

Date Revised 13.08.2019

published: Print

Citation Status MEDLINE

Förderinstitution / Projekttitel:

PPN (Katalog-ID):

NLM000098523