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Enzymatic Formation of Udp-N-Acetylgalactosamine in Epiphysial-Plate Cartilage

1978; Taylor & Francis; Volume: 6; Issue: 2 Linguagem: Inglês

10.3109/03008207809152615

1607-8438

Giancarlo De Luca, Simonetta Rindi, A. Castellani,

Polyamine Metabolism and Applications

The activity of UDP-N-acetylglucosamine 4'-epimerase (EC 5.1.3.7) from newborn pig epiphysial-plate cartilage was investigated. The formation of radioactive UDP-N-acetylgalactosamine from UDP-N-acetyl[U-14C]-glucosamine was demonstrated by radioautography, after hydrolysis of UDP-derivatives and separation of the hexosamines by paper chromatography. The pH optimum and the Km values for UDP-N-acetylglucosamine and NAD were determined. At equilibrium, the ratio UDP-N-acetylglucosamine/UDP-N-acetylgalactosamine reaches a value of about 2.3. The effect of UDP-xylose and UDP-glucuronic acid on the enzyme activity was investigated. NADH inhibits UDP-N-acetylglucosamine 4'-epimerase activity. The inhibitory effect of NADH seems to be strikingly correlated with the value of NAD/NADH ratio and pH.