Effect of chemical modification on structure and activity of glucoamylase from Aspergillus candidus and Rhizopus species.

Shenoy, B. C. and Appu Rao, A. G. and Raghavendra Rao, M. R. (1987) Effect of chemical modification on structure and activity of glucoamylase from Aspergillus candidus and Rhizopus species. Journal of Biosciences, 11 (1-4). pp. 339-350.

PDF J. Biosci., Vol· 11, Numbers 1–4, March 1987, pp· 339-350.pdf - Published Version Restricted to Registered users only Download (686kB) | Request a copy

Abstract

The histidine, tyrosine, tryptophan and carboxyl groups in the enzyme glucoamylase from Aspergillus Candidus and Rhizopus species were modified using group specific reagents. Treatment of the enzyme with diethylpyrocarbonate resulted in the modification of 0·3 and 1 histidine residues with only a slight loss in activity (10% and 35%) of glucoamylase from Aspergillus candidus and Rhizopus species respectively. Modification of tyrosine either by Nacetylimidazole or [I125]-leads to a partial loss of activity. Under denaturing conditions, maltose did not help in protecting the enzyme against tyrosine modification or inactivation. Treatment with 2-Hydroxy-5-nitro benzyl bromide in the presence of urea, photooxidation at pH 9·0, N-bromosuccinamide at pH 4·8 resulted in a complete loss of activity· However, the results of experiments in the presence of maltose and at pH 4·8 photooxidation and Nbromosuccinamide treatment suggested the presence of two tryptophan residues at the active site. There was a complete loss of enzyme activity when 10 and 28 carboxyl groups from Aspergillus candidus and Rhizopus, respectively were modified. Modification in the presence of substrate maltose, showed at least two carboxyl groups were present at the active site of enzyme and that only one active center seems to be involved in breaking ally 3 types of α-glucosidic linkages namely α-1,4, α-1, 6 and α-l,3.

Item Type:	Article
Uncontrolled Keywords:	Glucoamylases; chemical modification; structure and activity
Subjects:	500 Natural Sciences and Mathematics > 08 Botanical sciences > 01 Botany > 03 Fungi 600 Technology > 08 Food technology > 16 Nutritive value > 05 Enzymes
Divisions:	Protein Chemistry and Technology
Depositing User:	Food Sci. & Technol. Information Services
Date Deposited:	14 Mar 2018 04:04
Last Modified:	14 Mar 2018 04:04
URI:	http://ir.cftri.res.in/id/eprint/3852

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