Occurrence of Hydroxypyruvate—l-Glutamate Transaminase in Escherichia coli and Its Separation from Hydroxypyruvate-Phosphate—l-Glutamate Transaminase

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Blatt, L. (University of Wisconsin, Madison), F. E. Dorer, and H. J. Sallach. Occurrence of hydroxypyruvate–l-glutamate transaminase in Escherichia coli and its separation from hydroxypyruvate-phosphate–l-glutamate transaminase. J. Bacteriol. 92:668–675. 1966.—The formation of l-serine from hydroxypyruvate by a transamination reaction with l-glutamate has been demonstrated in extracts of Escherichia coli. The level of activity with hydroxypyruvate is approximately one-tenth that observed with hydroxypyruvate-phosphate in cell-free extracts. The transamination of hydroxypyruvate, but not hydroxypyruvate-phosphate, is inhibited by inorganic phosphate. No marked differences in the levels of activity with hydroxypyruvate were observed in extracts from bacteria grown under different conditions. Heat treatment of enzyme preparations at 65 C rapidly destroys the activity with hydroxypyruvate-phosphate, but not that with hydroxypyruvate. Fractionation of extracts with lithium sulfate and alumina Cγ resulted not only in a 10-fold purification, but also in a complete separation of the two activities, thereby establishing that two different enzymes are involved in the transamination of hydroxypyruvate and hydroxypyruvate-phosphate. Hydroxypyruvate transaminase is present in two mutants that require serine for growth. The inability of hydroxypyruvate to replace the growth requirement for serine, even to a limited extent, was shown to be due to the inability of the bacteria to accumulate this compound actively.

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