THE ENZYMOLOGY OF LYSINE BIOSYNTHESIS IN HIGHER PLANTS. DIAMINOPIMELATE DECARBOXYLASE FROM WHEAT GERM

Abstract
Diaminopimelate decarboxylase (EC 4.1.1.20) has been purified 173-fold from extracts of wheat germ acetone powder. The enzyme has a pH optimum of 7.0 in phosphate buffer and a Km for diaminopimelate of 0.14 mM. There is an absolute requirement for activity of added pyridoxal phosphate. The Km for pyridoxal phosphate is 5.2 μM. Once the enzyme is exposed to pyridoxal phosphate, it is bound very tightly. The enzyme has a molecular weight of 75,000 as determined by gel filtration. L-Lysine inhibits the reaction but only at quite high concentration. This would not appear to be the enzyme whose regulation controls the production of lysine in wheat germ.

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