Comparative study of free and membrane-bound acidic beta-D-glucosidase from the hepatopancreas of the shrimp Penaeus japonicus (Crustacea: decapoda).
l. In the hepatopancreas of the shrimp Penaeus japonicus the beta-glucosidase is present, either free or membrane-bound. The specific activity of the purified enzyme is 237,333 units/mg of protein and 191,111 units/mg of protein for the free and the membrane-bound beta-glucosidase, respectively. 2.The non-membrane-bound beta-glucosidase appears to be the same molecular size as the membrane-bound enzyme, both being monomers and consisting of a polypeptide chain of apparent M(r) 65,000, as estimated by chromatography on Superose 12 and by SDS-PAGE. 3.Both enzymes share similarities in their molecular size and substrate specificities (with ratios of 100:17:4:12 for the non-membrane-bound and 100:32:13:12 for the membrane-bound enzyme for the activities with methylumbelliferyl-beta-D-glucoside, methylumbelliferyl-beta-D-galactoside, methylumbelliferyl-alpha -L-arabinopyranoside and methylumbelliferyl-beta-xyloside respectively, as substrates). 4.The membrane-bound beta-glucosidase can be differentiated from the non-membrane-bound enzyme by its isoelectric point (7.5 vs 6.6), Km (182 micrometer vs 76 micrometer), pH optimum (4.5 vs 5.5), phosphorylation,sialyation and thermostability.
Division of Biochemistry and Molecular Science, Institute of Zoology, Academia Sinica, Nankang, Taipei,Republic of China.
N N
NN
Chuang
J D
JD
Huang
K S
KS
Lin
D000818:Animals; D004591:Electrophoresis, Polyacrylamide Gel; D043143:Hepatopancreas / Q000201:enzymology; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D007525:Isoelectric Focusing; D008565:Membrane Proteins / Q000378:metabolism*; D008970:Molecular Weight; D033561:Penaeidae / Q000201:enzymology*; D010766:Phosphorylation; D013379:Substrate Specificity; D013997:Time Factors; D001617:beta-Glucosidase / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*
D008565:Membrane Proteins; D001617:beta-Glucosidase