A limiting factor in the depletion of plasma tyrosine following tyrosine phenol-lyase injection into normal mice was found to be the availability of an essential cofactor, pyridoxal phosphate. Because of the extremely short half-life of this cofactor, adequate elevation of circulating cofactor levels for prolonged periods by injection of a pyridoxal phosphate solution was not practical. Similar...

The unfolding of cytoplasmic aspartate aminotransferase from pig heart in solutions of guanidinium chloride (GdnHCl) was studied. Data from protein fluorescence, c.d. and thiol-group reactivity indicated that the enzyme was unfolded in 6 M-GdnHCl. Spectroscopic studies showed that this unfolding was accompanied by dissociation of the pyridoxal 5'-phosphate cofactor. On dilution of the GdnHCl, r...

Dempsey, Walter B. (University of Florida, Gainesville). Synthesis of pyridoxine by a pyridoxal auxotroph of Escherichia coli. J. Bacteriol. 92:333-337. 1966.-A pyridoxal auxotroph of Escherichia coli B produced pyridoxol and pyridoxol 5'-phosphate during starvation for pyridoxal. The identification of these compounds was made both by bioassay and by ion-exchange chromatography. Pyridoxol 5'-ph...

A new method has been developed for the assay of serum pyridoxal using L. casei. Bound pyridoxal phosphate in serum is converted by acid hydrolysis to pyridoxal for which this organism is specific. This method proved to be considerably more sensitive than other methods so far reported in the literature. Serum pyridoxal concentrations were measured in 151 control subjects aged 17 to 80 years. Th...

A timeand concentration-dependent irreversible inactivation of the Escherichia coli biodegradative threonine dehydratase by glyoxylate is accompanied by enzyme aggregation, apparent covalent binding of 4 mol of glyoxylate/mol of aggregated species, and a displacement of the absorption maximum of the enzyme-bound pyridoxal phosphate from 413 to 388 nm (Park, L. S., and Datta, P. (1979) J Biol. C...

To probe the structural and functional roles of activesite residues in the tryptophan synthase a2b2 complex from Salmonella typhimurium, we have determined the effects of mutation of His in the b subunit. His is located adjacent to b subunit Lys, which forms an internal aldimine with the pyridoxal phosphate and catalyzes the abstraction of the a-proton of L-serine. The replacement of His by leu...

Iterative profile sequence analysis reveals a remote homology of peroxisomal serine-pyruvate aminotransferases from mammals to the small subunit of soluble hydrogenases from cyanobacteria, an isopenicillin N epimerase, the NifS gene products from bacteria and yeast, and the phosphoserine aminotransferase family. All members of this new class whose function is known are pyridoxal phosphate-depen...

The plasma pyridoxal phosphate concentration was determined in 30 cases of early breast cancer, 21 patients with locally recurrent disease, and 43 patients with systemic metastases. The two groups of advanced breast cancer had significantly lower plasma pyridoxal phosphate levels than 36 healthy women of similar age. Urinary 4-pyridoxic acid excretion was normal in breast cancer. Plasma pyridox...

The authors reported earlier (1) that the crystalline homoaerine deaminase-cystathionase prepared from rat livers contained pyridoxal-5-phosphate as the prosthetic group, and that the bound pyridoxal-5-phosphate is responsible for the absorption maximum at 427 rnp. The present paper deals with resolution of the enzyme into pyridoxal-5-P and catalytically inactive apoenzyme, and the subsequent r...

There is ample experimental evidence which indicates that 4-aminobutyric acid is an inhibitory neurotransmitter in mammalian brain. Changes in 4-aminobutyric acid concentrations in the central nervous system have therefore prompted speculation regarding its involvement in neurological aberrations. Individuals homozygous for cystathionine /3-synthase deficiency (an autosomal recessive inherited ...