1994 Volume 68 Issue 8 Pages 423-434
The intracellular proportion of the pyridoxal 5'-phosphate (PLP) form of aspartate aminotransferase (AspAT) to the total enzyme in E. coli B cells and rabbit erythrocytes was determined by a newly devised method which based on selective inactivation of PLP form of AspAT by sodium borohydride added extracellularly. A large portion (80-90% and 75%) of the intracellular AspAT was in PLP form in E. coli cells and the erythrocytes, respectively. The saturation levels generally used to describe in vivo the proportion of the apo and holo vitamin B-6-dependent enzymes did not reflect the intracellular amount of PLP (holo) form of AspAT. The interaction between PLP form of AspAT and vitamin B-6 antagonists were studied in situ. The concentration of vitamin B-6 compounds in the erythrocytes and effects of the antagonists on the concentration of vitamin B-6 compounds were also determined after the erythrocytes were incubated with free vitamin B-6 compounds.
