Composition and synthesis of gangliosides in rat hepatocyte and hepatoma cell lines.

The dehydroalanine present in histidine ammonia lyase is essential for the activity of this enzyme, and may be at the active site. This was shown by recovery of 3H-alanine4 and loss of activity on reduction of the enzyme with NaBaH4, and by protection of both reduction and inactivation by histidine. Since several pyruvate-containing enzymes have been described recently (1P17), it is important to note that no 3H-lactate was found in acid hydrolysates of NaB3H4-reduced histidine ammonia lyase. Spectral studies and attempts to resolve the enzyme away from a cofactor (3, 4) have failed to give evidence for the presence of pyridoxal phosphate.