Synechococcus mutants resistant to an enamine mechanism inhibitor of glutamate-1-semialdehyde aminotransferase

An enamine mechanism-based inactivator of mammalian delta-aminobutyric acid aminotransferase, I-amino 5-fluoropentanoic acid is a potent inhibitor of cell growth and pigment formation in the cyanobacterium Synechococcus PCC 6 301, It was demonstrated that 4-amino 5-fluoropentanoic acid inhibits the a minolaevulinate synthesis at glutamate l-semialdehyde aminotransferase and that in the mutant obtained by exposing cells to 40 mu M 4-amino 5-fluorope ntanoic acid, this enzyme was insensitive to the inhibitor. The specific ac tivity of glutamate 1-semialdehyde aminotransferase in cell extracts was lo wer in the mutant, although the cell growth rate was unaffected, The decrea se in sensitivity to 4-amino 5-fluoropentanoic acid in the mutant is due to a structural gene mutation, a single base change in the hemL gene resultin g in a S162T substitution in the gene product. (C) 1999 Federation of Europ ean Biochemical Societies.