A neutral beta-galactosidase from the hepatopancreas of the shrimp Penaeus monodon (Crustacea: Decapoda): dimeric and sialyated.
1. A beta-galactosidase was purified ca 245-fold to homogeneity from Penaeus monodon, with a final spec. act. of 61.3 U/mg of protein. 2.By using SDS-polyacrylamide gel electrophoresis, the monomers of shrimp beta-galactosidase were discovered to have mol. wts of 31,000 and those of human placental enzyme, 32,000. Since the active shrimp beta-galactosidase was found to have a mol. wt of 66,000 by AcA 34 gel filtration chromatography,it was concluded that the purified shrimp enzyme was dimeric. 3.In contrast to the discovery of thermostability with human placental beta-galactosidase, the shrimp enzyme was found to be unstable to heating at 45 degree C for 10 min. Both enzyme activities were inhibited by Mn (2+) and Zn (2+) ions.4. The shrimp beta-galactosidase has an isoelectric point (pI) of 7.0, but the human placental enzyme has a pI of 5.5. Both enzymes were sialyated. 5.The shrimp beta-galactosidase has a pH optimum at 7.0 and its K(m) was 1.9 micrometer with 4-methylumbelliferyl-beta-D-galactoside as substrate. The human enzyme has pH optimum at 7.0 or 4.0, and its K(m) was 9.8 micrometer.
Chuang
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Division of Biochemistry and Molecular Science, Institute of Zoology, Academia Sinica,Nankang, Taipei, R. of China.
D000818:Animals; D004591:Electrophoresis, Polyacrylamide Gel; D004795:Enzyme Stability; D043143:Hepatopancreas / Q000201:enzymology; D006358:Hot Temperature; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007526:Isoelectric Point; D008970:Molecular Weight; D033561:Penaeidae / Q000201:enzymology*; D001616:beta-Galactosidase / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*
D001616:beta-Galactosidase