Occurrence of a Malic Enzyme free of Oxalacetic Decarboxylase in Silkworm Hæmolymph

Abstract

HÆMOLYMPH of the larval silkworm (Bombyx mori L.) contains a triphosphopyridine nucleotide-linked ‘malic’ enzyme that has been purified by ammonium sulphate fractionation followed by adsorption and elution from calcium phosphate gel^1,2. It was of interest to measure the oxalacetic decarboxylase activity of the ‘malic’ enzyme from silkworm, since those of pigeon liver^3,4 and wheat germ^5,6 exhibit a constant ratio (approximately 1.2 : 1) between oxalacetic decarboxylase and ‘malic’ enzyme activities throughout all stages of their purification. Recently, a diphosphopyridine nucleotide-linked ‘malic’ enzyme free of oxalacetic decarboxylase was purified from homogenates of Ascaris lumbricoides ⁷. ‘Malic’ enzyme activity has been reported in crude homogenates of larvæ from the blowfly⁸. These extracts also decarboxylate oxalacetate; but it has not yet been established whether both reactions are catalysed by the same enzyme.