ISOLATION AND CHARACTERIZATION OF METHYLMALONYL-COA MUTASE FROM HUMAN-PLACENTA

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  • 1 January 1980
    • journal article
    • research article
    • Vol. 255  (7) , 2708-2712
Abstract
Methylmalonyl-CoA mutase, one of 2 known cobalamin-dependent enzymes present in mammalian tissues, was isolated from 2.5 kg of human placenta utilizing affinity chromatography on 5''-deoxyadenosylcobalamin-Sepharose as the major purification step. The enzyme gives a single band on polyacrylamide disc gel electrophoresis. The MW of the enzyme is 145,000 and it has 2 subunits of MW = 72,000. Amino acid analysis reveals major differences from other human cobalamin-binding proteins. Based on X-ray fluorescence, the enzyme has 2 mol of cobalamin bound/mol of enzyme. In contrast to purified cobalamin transport proteins, most of the cobalamin bound to the enzyme is not released by boiling at low pH in the presence of KCN, or dialysis against 7.5 M guanidine containing 0.2 M dithiothreitol, or both, suggesting the possibility that cobalamin may be covalently attached to the purified enzyme. Both precipitating antibodies and antibodies that inhibit enzyme activity were raised in a chicken.