Cell-free extracts of Neurospora crassa mycelium catalyze the methylation of l-histidine to form hercynine (histidine betaine). The partially methylated compounds, alpha-N-methyl-l-histidine and alpha-N,N-dimethyl-l-histidine, are also methylated by the same enzyme preparation to form hercynine. All three methylation reactions are stimulated by the addition of S-adenosylmethionine.

The present study deals with the application of high-performance-liquid-chromatography (HPLC) method for a quantitative detection of carnosine, anserine, L-histidine and 3-methyl-L-histidine in biological material with o-phthaldialdehyde (OPA) post column derivatisation at the constant temperature of 50 degrees C. For this purpose, some mobile-phases were prepared with scalar acetonitrile conce...

Inbred weanling rats were maintained on diets containing low (6%), medium (lS%), and high (40%) levels of proteins. After 45 days they were killed and the activities of histidine ammonia lyase, urocanase, and histidine pyruvate aminotransferase in liver were assayed. Histidine ammonia lyase increased with age of the rat, and the increase was proportional to the level of protein in the diet. Ani...

Inbred weanling rats were maintained on diets containing low (6%), medium (lS%), and high (40%) levels of proteins. After 45 days they were killed and the activities of histidine ammonia lyase, urocanase, and histidine pyruvate aminotransferase in liver were assayed. Histidine ammonia lyase increased with age of the rat, and the increase was proportional to the level of protein in the diet. Ani...

EnvZ and OmpR are the sensor and response regulator proteins of a two-component system that controls the porin regulon of Escherichia coli in response to osmolarity. Three enzymatic activities are associated with EnvZ: autokinase, OmpR kinase, and OmpR-phosphate (OmpR-P) phosphatase. Conserved histidine-243 is critical for both autokinase and OmpR kinase activities. To investigate its involveme...

Zinc is an essential trace element involved in a wide range of biological processes and human diseases. Zinc excess is deleterious, and animals require mechanisms to protect against zinc toxicity. To identify genes that modulate zinc tolerance, we performed a forward genetic screen for Caenorhabditis elegans mutants that were resistant to zinc toxicity. Here we demonstrate that mutations of the...

Dog bone marrow nucleated cells were incubated in media containing labeled L-amino acids, and the cellular accumulation of radioactivity as a function of time was measured and analyzed according to a three-compartment model.(a) The turnover half-time of intracellular histidine arising from extracellular sources was 6.0 +/-0.7 (SEM) min. Similar turnover half-time for serine was 10 +/-2 (SEM) mi...

We have examined the effects of prolonged histidine deprivation on the reversion of Salmonella typhimurium histidine auxotrophs containing either hisG46, a missense mutation (CTC----CCC), or hisG428, an ochre mutation (CAA----TAA). Both of these mutants can revert to His+ via intragenic and extragenic mechanisms. Whereas the hisG46 mutant site consists of G/C base pairs, extragenic suppression ...

Streptomyces coelicolor mutant RF-59, isolated as a revertant of a histidine auxotroph after mutagenic treatment with N-methylN'-nitro-N-nitrosoguanidine, was found to accumulate L-histidine. The mutant was sensitive to 2-thiazo-lealanine and L-2,4-diaminobutyric acid and partially sensitive to alpha-methylhistidine but resistant to 1,2,4-triazolealanine, indicating that repression of the histi...

The basic amino acid histidine inhibited yeast cell growth more severely than lysine and arginine. Overexpression of CTR1, which encodes a high-affinity copper transporter on the plasma membrane, or addition of copper to the medium alleviated this cytotoxicity. However, the intracellular level of copper ions was not decreased in the presence of excess histidine. These results indicate that hist...