SUBSTRATE-SPECIFICITY OF RAINBOW-TROUT TESTIS CMP-3-DEOXY-D-GLYCERO-D-GALACTO-NONULOSONIC ACID (CMP-KDN) SYNTHETASE - KINETIC-STUDIES OF THE REACTION OF NATURAL AND SYNTHETIC ANALOGS OF NONULOSONIC ACID-CATALYZED BY CMP-KDN SYNTHETASE

In this report we present kinetic data of the activation reaction of s everal synthetic 3-deoxy-D-glycero-D-galacto-nonulosonic acid (Kdn) an d N-acetylneuraminic acid (Neu5Ac) analogues catalyzed by the rainbow trout testis CMP-Kdn synthetase. This enzyme showed broad substrate sp ecificity in terms of substitutions at C4 or C5 position of Kdn and Ne u5Ac. In contrast, calf brain CMP-N-acylneuraminic acid synthetase had narrow substrate specificity, being active only on various N-acyl ana logues of NeuSAc and only slightly active on Kdn derivatives. Usefulne ss of the trout testis enzyme for synthesis of various CMP-sialate ana logues, which could be donor substrates for sialyltransferases, was de monstrated.