The B subunit can catalyze Reaction 1 even in the absence of Subunit A (5). Reaction 2 can be catalyzed similarly by the A subunit alone (2). Both Reaction 1 and Reaction 2 proceed best, however, when catalyzed by the complex formed from the two subunits (2). Reaction 3 takes place only in the presence of the AB complex; apparently indole is not a free intermediate in this reaction (2). The A p...

Background: 1-Deoxy-D-xylulose 5-phosphate (DXP) synthase is a thiamine diphosphate (ThDP)dependent enzyme in pathogen isoprenoid biosynthesis and a potential drug target. Results: Tryptophan fluorescence and kinetic analyses show that donor and acceptor substrates bind reversibly and independently to DXP synthase. Conclusion: DXP synthase catalyzes a novel, ThDP-dependent, random sequential me...

Tissue tropism of clinical ocular and genital Chlamydia trachomatis strains is shown to be linked to the tryptophan synthase genotype. It is suggested that, in the presence of IFN-gamma, which depletes available tryptophan, there exist unique host-parasite interactions that may contribute to persistent chlamydial infection.

Suppressors of the blue fluorescence phenotype of the Arabidopsis trp7-700 mutant can be used to identify mutations in genes involved in plant tryptophan biosynthesis. Two recessive suppressor mutations define a new gene, TRP4. The trp4 mutant and the trp7-700 mutant are morphologically normal and grow without tryptophan, whereas the trp4; trp7700 double mutant requires tryptophan for growth. T...

Seventy-nine 5-methyltryptophan-resistant cell lines have been selected from haploid Datura innoxia Mill. cell cultures by plating suspensions in agar medium containing a growth inhibitory concentration of 5-methyltryptophan. Mutagen treatment increased the frequency of resistance. The eleven variants tested posses an altered anthranilate synthase less sensitive to feedback inhibition by trypto...

Arabidopsis thaliana has two genes, ASA1 and ASA2, encoding the alpha subunit of anthranilate synthase, the enzyme catalyzing the first reaction in the tryptophan biosynthetic pathway. As a branchpoint enzyme in aromatic amino acid biosynthesis, anthranilate synthase has an important regulatory role. The sequences of the plant genes are homologous to their microbial counterparts. Both predicted...

BACKGROUND L-tryptophan is an important ingredient in medicines, especially in neuromedicines such as antidepressants. Many commercial processes employ various microorganisms with high tryptophan synthase activity to produce L-tryptophan from indole and L-serine, but these processes are very costly due to the costs of precursors, especially L-serine. OBJECTIVES For this reason, we studied the...

A direct relation between gene dosage and amount of the corresponding protein is generally assumed to exist though it has been investigated in a limited number of cases. Yeasts seem to be an ideal material for this type of investigation as they can be easily obtained in different degrees of ploidy. Macromolecular components of yeast cells in polyploid series have been already determined (OGUR e...