PURIFICATION OF A MOLYBDOCOFACTOR-CONTAINING PROTEIN FROM PEA-SEEDS AND IDENTIFICATION OF MOLYBDOPTERIN

A molybdenum cofactor-containing protein (MCCP) was purified from pea (Pisum sativum L.) seeds. The purified protein was shown to be electro phoretically homogeneous, of 300 kDa with subunits of 150 kDa molecula r mass and a pi of 5.0 (as determined by isoelectric focusing). The pr otein dimer contained two molecules of molybdopterin (MPT). The molybd enum cofactor (Moco) was identified as mononucleotide. Molybdenum cofa ctor activity could be detected only after heat treatment under protec tion of reduced glutathione and EDTA. Exogenous molybdate was essentia l for Moco determination, thus suggesting that Moco from seeds MCCP wa s free (''empty'') of molybdenum.