Increased tyrosine phenol-lyase activity in mice following pyridoxal phosphate administration.
A limiting factor in the depletion of plasma tyrosine following tyrosine phenol-lyase injection into normal mice was found to be the availability of an essential cofactor, pyridoxal phosphate. Because of the extremely short half-life of this cofactor, adequate elevation of circulating cofactor levels for prolonged periods by injection of a pyridoxal phosphate solution was not practical. Similarly, long-term diets enriched with pyridoxine and pyridoxal phosphate did not significantly improve the efficiency of the injected holoenzyme. A repository dosage form was devised that consisted of an s.c. implant of pyridoxal phosphate suspended in a spermaceti and peanut oil mixture. Under these conditions a sustained increase in holoenzyme activity levels and a significant resulting decrease in plasma tyrosine levels were obtained.
D000818:Animals; D003692:Delayed-Action Preparations; D005260:Female; D008190:Lyases / Q000097:blood*; D008545:Melanoma / Q000188:drug therapy* / Q000201:enzymology; D051379:Mice; D008810:Mice, Inbred C57BL; D008811:Mice, Inbred DBA; D009374:Neoplasms, Experimental / Q000188:drug therapy; D011732:Pyridoxal Phosphate / Q000008:administration & dosage*; D014447:Tyrosine Phenol-Lyase / Q000097:blood*
D003692:Delayed-Action Preparations; D011732:Pyridoxal Phosphate; D008190:Lyases; D014447:Tyrosine Phenol-Lyase