Lipid‐dependent membrane enzymes

1 Diacylglycerol kinase apoprotein was purified from membranes of Escherichia coli K12 by a six‐step procedure that included HPLC. The proposed assignment of the enzyme to the dgkA gene [Lightner et al. (1983) J. Biol. Chem. 258 , 10856–10861] could be supported by molecular mass determination (∼ 14 kDa), N‐terminal sequencing (Met‐Ala‐Am), cyanogen bromide fragmentation and amino acid analysis. As predicted, proline was absent. 2 The membrane‐associated as well as the butan‐1‐ol‐dissolved enzyme survived heating to 100 °C. 3 Alkylglycoside detergents were found to constitute an additional class of lipid activators. 4 The enzyme apoprotein in a non‐activating substrate/detergent solution was capable of autocatalytic self‐activation which was attributed to a novel feedback activation mechanism involving phosphatidic acid (diacylglycerol 3‐phosphate).