Zur Biosynthese der Glykolyl-Gruppe der N-Glykolyl-neuraminsäure. Die oxydative Umwandlung der N-Acetyl-Gruppe zur Glykolyl-Gruppe

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Abstract
Slices of bovine and porcine submaxillary gland were incubated with N-[ 1-14C]acetyl-glucosamine, [ 1-14C] glucosamine and [u-14C] glucose. Radioactivity was incorporated into the various acylneuraminic acids, which were then resolved by ion exchange and cellulose chromatography. Labeled N-acetyl-O-acetylneuraminic acid, N-acetyl- and N-glycolylneuraminic acid were isolated from the bovine system, and labeled N-acetyl- and N-glycolylneuraminic acid from the porcine system. The acyl groups of the acylneuraminic acids were converted into acylate esters, which were then separated by distillation. It was thus possible to determine the distribution of radioactivity between the carbon chain and the acyl groups of the acyl-neuraminic acids. After incubation with [u-14C] glucose and [ 1-14C] -glucosamine, the acyl neuraminic acids were labeled essentially in the neuraminic acid moiety. After the incubation with N-[ 1-14C]acetyl-glucosamine the acetyl group of N-acetylneuraminic acid became labeled, but there was also considerable radio-activity in the glycolyl group of the N-glycolyl-neuraminic acid; the 9-carbon chain of the neuraminic acid remained practically unlabeled. These observations can only be explained by an oxidation of the N-acetyl group to give the N-glycolyl group. The existence of an "N-acetyl-hydroxylase" is claimed, and it is proposed that the mechanism of oxidation is analogous to that of the steroid-C19 or -C21 hydroxylases (EC 1. 99. 1. 10, or 11).

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