Tryptophan Biosynthetic Enzymes of Staphylococcus aureus

Abstract

Tryptophan biosynthetic enzymes were assayed in various tryptophan mutants of Staphylococcus aureus strain 655 and the wild-type parent. All mutants, except trpB mutants, lacked only the activity corresponding to the particular biosynthetic block, as suggested previously by analysis of accumulated intermediates and auxonography. Tryptophan synthetase A was not detected in extracts of either trpA or trpB mutants but appeared normal in other mutants. Mutants in certain other classes exhibited partial loss of another particular tryptophan enzyme activity. Tryptophan synthetase B activity was not detected in cell extract preparations but was detected in whole cells. The original map order proposed for the S. aureus tryptophan gene cluster was clarified by the definition of trpD (phosphoribosyl transferase − ) and trpF (phosphoribosyl anthranilate isomerase − ) mutants. These mutants were previously unresolved and designated as trp ( DF ) mutants (anthranilate accumulators). Phosphoribosyl anthranilate isomerase and indole-3-glycerol phosphate synthetase enzymes were separable by molecular sieve chromatography, suggesting that these functions are coded by separate loci. Molecular sieve chromatography failed to reveal aggregates involving anthranilate synthetase, phosphoribosyl transferase, phosphoribosyl anthranilate isomerase, and indole-3-glycerol phosphate synthetase, and this procedure provided an estimate of the molecular weights of these enzymes. Tryptophan was shown to repress synthesis of all six tryptophan biosynthetic enzymes, and derepression of all six activities was incident upon tryptophan starvation. Tryptophan inhibited the activity of anthranilate synthetase, the first enzyme of the pathway.

Comparative proteomic investigation of multiple methicillin-resistant Staphylococcus aureus strains generated through adaptive laboratory evolution

“…From the GO analysis ( Figures 4 C and 4E), tryptophan synthase activity was the most up-regulated molecular function in both S1D14 and S3D14 (fold enrichment above 30 folds), suggesting that the level of tryptophan is possibly higher in S1D14 and S3D14 than in the ancestral strain. Since tryptophan was known to inhibit the activity of anthranilate synthase ( Proctor and Kloos, 1973 ), the increased expression of this protein in S1D14 and S3D14 may be a response to counteract the inhibition of its activity by increased levels of tryptophan.…”

Gene rearrangements in the evolution of the tryptophan synthetic pathway.

“…Chromosomal arrangement. Proctor and Kloos (168,169) used transduction to study a group of Staphylococcus aureus tryptophan auxotrophs blocked at various points in the pathway. All their mutants were linked, and by quantitative recombination experiments they determined the gene order to be trpE, D, C, F, B, and A (Fig.…”

“…Proctor and Kloos (169) studied the tryptophan enzyme levels in trpA and trpE auxotrophs of S. aureus grown under conditions of tryptophan excess or limitation. They found that all five enzymes (both the A and B reactions of TS were studied, so six specific activities were measured) were derepressed concurrently and coordinately upon tryptophan starvation.…”

Enzymes of the Tryptophan Pathway in Three Bacillus Species

“…When methods for stabilizing these enzymes in cell-free extracts were developed, it became apparent that they are coordinately regulated (14). B. subtilis was the first gram-positive bacterium in which these enzymes were examined in detail, although the pathway has now been studied in Staphylococcus aureus (21) and the anaerobe Clostridium butyricum (2) as well. Of course, the genes and enzymes of the tryptophan pathway have been extensively investigated in a number of gram-negative organisms, including Escherichia coli (5) and other enteric organisms, Pseudomonas putida (6), Chromobacterium violaceum (29), and Acinetobacter calcoaceticus (24,28).…”