INDICATIONS FOR THE ENZYMATIC-SYNTHESIS OF 9-O-LACTOYL-N-ACETYLNEURAMINIC ACID IN EQUINE LIVER

Fractionation of horse liver homogenate by centrifugation into heavy m embranes at 10000 x g, microsomal fraction at 105 000 x g, and the sup ernatant revealed sialate 9-O-lactoyltransferase activity only in the latter fraction. For the enzyme assay, the various fractions were incu bated with C-14 labelled CMP-N-acetylneuraminic acid, N-acetylneuramin ic acid and glycoconjugate-bound N-acetylneuraminic acid. Lactoylation was identified in three different TLC systems after acid hydrolysis a nd purification of the sialic acids in the incubation mixtures. Enzyme activity was found only in the supernatant fraction. Glycoconjugate-b ound N-acetylneuraminic acid was the best substrate tested, although s ome lactoylation was also found when using CMP-N-acetylneuraminic acid .