A G Appu Rao
Articles written in Journal of Biosciences
Volume 4 Issue 2 June 1982 pp 197-208
The major protein from glanded cottonseed has been isolated in a homogeneous form. Its S20 w value at 1 protein concentration is 6S in 1 M NaCl solution. It contains 1 carbohydrate and is free from phosphorus, gossypol (bound or free) and nucleic acid impurities. It consists of atleast seven non-identical subunits. The protein has an ultraviolet absorption maximum at 278 nm and fluorescence excitation and emission maxima at 280 nm and 325 nm respectively. Optical rotatory dispersion and circular dichroism measurements indicate that the protein consists predominantly of Β-structure and random coil. The observed near-ultraviolet circular dichroic bands can be attributed to tyrosine, phenylalanine and tryptophan residues of the protein.
Volume 6 Issue 5 December 1984 pp 601-611
Glucoamylase II (EC 18.104.22.168) from
Volume 7 Issue 3-4 June 1985 pp 399-419
The purification and properties of glucoamylase (α-l,4-glucan glucohydrolase, EC 22.214.171.124) from different fungal sources have been compared. The studies on the conformation and activity of the native enzyme at a function of pH, temperature, substrate concentration and the effect of denaturants and on the role of carbohydrate moiety on structure and stability have been reviewed. The chemical modification of the active centre, binding kinetics of the substrate and active site and the mechanism of action have been summarized. They differ in their fine structure as revealed by their near ultra-violet circular dichroism spectra and contain 30–35 % α-helix, 24–36 %
The glucoamylases are glycoprotein in nature, differ in their content and nature of carbohydrate from different sources. The carbohydrate moiety plays an important role in stabilising the native conformation of the enzyme and is not involved in activity and antigenecity.
At the active site of the enzyme, two tryptophan and two carboxyl (glutamate or aspartate) groups are present. It is likely that the histidine and tyrosine residues which are present away from the active site are involved in binding of the substrate. There seems to be seven subsites which are involved in binding of the substrate and the catalytic site is situated in between 1 and 2 subsites. In breaking of α-1,4-, α-1,3-, and α-l,6-bonds only one active centre is involved.
Studies on the immobilization of either glucoamylase alone or as a part of a multienzyme system have been reviewed briefly
Volume 11 Issue 1-4 March 1987 pp 339-350
The histidine, tyrosine, tryPtoPhan and carboxyl grouPs in the enzyme glucoamylase from