Gene rearrangements in the evolution of the tryptophan synthetic pathway.

Abstract

INTRODUCTION .88 DESCRIPTION OF THE PATHWAY .88 Reactions .88 Regulation of Metabolite Flow .89 Feedback inhibition .89 Repression of enzyme synthesis .89 Early Evolutionary Speculations .90 ENTEROBACTERIACEAE.90 Operon Structure. go Genetic studies .90 Messenger RNA studies .91 Regulatory mutations .91 Polarity and antipolarity .92 Deviations from Coordinacy .93

VII. Yeast sequencing reports. Complete sequence of the Saccharomyces cerevisiae LEU1 gene encoding isopropylmalate isomerase

“…Even though the bacterial LEUC gene has not yet been sequenced it is likely that the yeast isopropylmalate isomerase gene has evolved from the fusion of the two genes LEUC and LEUD which are separated in bacteria. A similar event has already been described (Crawford, 1975 and references therein) for tryptophan synthase, which in Escherichia coli, comprises the alpha and beta chains encoded by two separate genes, while in Saccharomyces cerevisiae this enzyme is coded by only one gene.…”

Organization and regulation of genes for amino acid biosynthesis in lactic acid bacteria

“…This analysis ( Table 2) characterized biosynthetic genes with amino acid sequences identical to those of known biosynthetic enzymes in the range of 26-54%. Such conservation is not surprising since biosynthetic genes are highly conserved during evolution [22]. Most of them were also identified by complementation tests using E. coli and B. subtilis mutants ( Table 2).…”

“…Conversely, in the absence of sufficient exogenous supply, biosynthesis should be rapidly induced and coordinated to achieve optimized growth of the cells. The study of amino acid biosynthetic pathways may also help in understanding the reasons for the fastidiousness of 22 lactic acid bacteria which makes them unable to grow unless certain amino acids are supplied in the medium. This differentiates them from other bacterial species like Escherichia col± or Bacillus subtilis which can grow on minimal media containing only mineral salts and glucose.…”

Crystallization and preliminary X‐ray crystallographic data of the bifunctional enzyme phosphoribosyl‐anthranilate isomerase—indole‐3‐glycerol‐phosphate synthase from Escherichia coli

“…In Bacillus subtilis and Pseudomonas putida the reactions are catalyzed by 2 separate enzymes [4-61 while in Brevibacterium fravum they form a multienzyme complex [7]. Such diversity of organization has prompted the suggestion that evolution may have progressed from single function enzymes via multienzyme complexes to multifunctional enzymes [8]. Limited proteolysis studies with E. coli PRAI-InGPS have shown that an N-terminal fragment catalyzes the InGPS reaction, while a C-terminal fragment independently catalyzes the PRAI reaction [9].…”