Feb 25, 1976

Transport and metabolism of vitamin B6 in the yeast Saccharomyces carlsbergensis 4228

The Journal of Biological Chemistry
B Shane, E E Snell

Abstract

Active transport of pyridoxine, pyridoxal, and pyridoxamine occurs in resting cells of Saccharomyces carlsbergensis 4228 and can lead to intracellular concentrations of free vitamin much higher than those supplied externally. The initial Km for pyridoxine uptake is 3.6 x 10(-7) M at 30 degrees and pH 4.5, which are optimum for growth. Transport is inhibited by many unphosphorylated vitamin analogs, the most effective being 5'-deoxypyridoxine, 5'-deoxypridoxal, toxopyrimidine, 4'-deoxypyridoxine, and 3-amino-3-deoxypyridoxine. Two distinct uptake systems that differ in structural specificity and ionic requirements are present. One, with optimum pH of 3.5, transports pyridoxal effectively, but not pyridoxamine; the other (optimum pH 6.0) transports pyridoxamine effectively, but not pyridoxal. Both systems transport pyridoxine, while neither transports pyridoxal 5'-phosphate. Other properties of these systems are similar, indicating that they share certain elements in common. An initial temperature optimum of 30 degrees is observed for pyrodoxine transport and, at this temperature, an "overshoot" in intracellular vitamin levels, with subsequent decrease to a constant level, occurs with time. It appears that intracellular vitamin, ...Continue Reading

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Mentioned in this Paper

Metabolic Process, Cellular
Toxopyrimidine
Structure-Activity Relationship
Protoplasm
Analog
Uptake
5'-deoxypyridoxine
Pyridoxal Phosphate
Glucose, (beta-D)-Isomer
Receptors, Drug

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