The ‘malic’ enzyme in insect blood

Abstract

Dialyzed silkworm blood contains a TPN-linked dehydrogenase that, in order of decreasing rates, reduces the following sugar phosphates to polyhydric-alcohol phosphates: ribose. 5-, galactose 6-, glucose 6- and fructose 6-phosphates. Synthesis of polyhydric alcohol phosphate can be accomplished by coupling the oxidation of malic acid with the reduction of the sugar phosphate in the presence of TPN and dialyzed silkworm blood. Phos-phohexoisomerase is present in silkworm blood; no ribose phosphate-isomerase activity was observed. The possibility is considered that polyhydric alcohol phosphate formation in the insect assists in the storage of metabolic energy.