Intracellular predominance of the pyridoxal 5'-phosphate form of aspartate aminotransferase in Escherichia coli B and reversible transformation of this form by extracellular substances

Biochimie
T YagiM Nozaki

Abstract

The intracellular proportion of the pyridoxal 5'-phosphate form of aspartate aminotransferase to the total enzyme in E. coli B cells was determined by a newly devised method, dependent on selective inactivation of the intracellular pyridoxal 5'-phosphate form of the enzyme by extracellularly added sodium borohydride. A large portion (80-99%) of the intracellular aspartate aminotransferase was in pyridoxal 5'-phosphate form in both natural and synthetic medium-grown bacterial cells. The intracellular predominancy of pyridoxal 5'-phosphate did not vary during the growth of bacteria and during incubation of bacterial cells in various kinds of buffers with different pH values. In contrast, the saturation levels generally used to describe in vivo the proportions of the apo and holo vitamin B6-dependent enzymes did not reflect the intracellular amount of the pyridoxal 5'-phosphate (holo) form of aspartate aminotransferase probably because the intracellular pyridoxal 5'-phosphate form was changed to an apo form by the disruption of bacterial cells for preparing crude extract. Various extracellularly-added vitamin B6 antagonists decreased the intracellular amount of pyridoxal 5'-phosphate without decrease in the total intracellular act...Continue Reading

References

Sep 27, 1979·Biochemical and Biophysical Research Communications·T YagiM Nozaki
Jan 1, 1974·Annual Review of Biochemistry·A L Goldberg, J F Dice
Aug 1, 1973·The Journal of Cell Biology·A H Huang, H Beevers
Jan 1, 1968·Analytical Biochemistry·P V Tishler, C J Epstein
Nov 1, 1982·Archives of Biochemistry and Biophysics·R D Reynolds
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Apr 29, 1983·Biochemical and Biophysical Research Communications·G M HartmeierB I Yang
Oct 13, 2001·Arteriosclerosis, Thrombosis, and Vascular Biology·M YehS T Reddy

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