To determine whether levodopa reduces the levels of S-adenosylmethionine in the human central nervous system, cerebrospinal fluid (CSF) concentrations of S-adenosylmethionine, methionine, 3-methoxytyrosine, levodopa and 5-methyltetrahydrofolate were measured in six children with dopamine deficiency before and after treatment. In four, the lack of dopamine was secondary to a reduction in concent...

The activities of liver transfer RNA (tRNA) methyltransferases from control or ovariectomized female rats were found to be higher than those of control or castrated males. Administration of testosterone to ovariectomized females caused activity to decrease to the level of the males. Conversely, administration of estrogen to castrated males resulted in liver enzyme levels similar to those of the...

An improved analytical method, based on high pressure liquid chromatography, has been developed for the simultaneous determination of the polyamines and S-adenosyl-containing compounds in extracts of plant protoplasts. The method involves simple procedures for sample preparation and permits quantification of 1 picomole or less for all the compounds. This method has been used to study the effect...

Asp kinase catalyzes the first step of the Asp-derived essential amino acid pathway in plants and microorganisms. Depending on the source organism, this enzyme contains up to four regulatory ACT domains and exhibits several isoforms under the control of a great variety of allosteric effectors. We report here the dimeric structure of a Lys and S-adenosylmethionine-sensitive Asp kinase isoform fr...

It has been shown that changes of intracellular levels of S-adenosylmethionine (SAM) are related to the well beings of cells and organisms. The fluctuation of SAM level is cause by imbalance between SAM synthesis and metabolic pathways (methylation, transsulfuration and aminiopropylation) or degradation. S-adenosylmethionine biosynthesis is strictly and solely dependent on the activity of Methi...

The biosynthesis of methionine from homocysteine may occur by transmethylation or through l-carbon addition from serine via tetrahydrofolate. It has been established that acetothetin, dimethyl-P-propiothetin, and betaine serve as methyl donors for the methylation of homocysteine in mammalian liver (l-3), but these compounds are inactive in microbial systems. The participation of S-adenosylmethi...

Many gram-negative bacteria synthesize N-acyl homoserine lactone autoinducer molecules as quorum-sensing signals which act as cell density-dependent regulators of gene expression. We have investigated the in vivo source of the acyl chain and homoserine lactone components of the autoinducer synthesized by the LuxI homolog, TraI. In Escherichia coli, synthesis of N-(3-oxooctanoyl)homoserine lacto...

Adjustment of polyamine contents in Escherichia coli was studied with strains of Escherichia coli producing normal (DR112) and excessive amounts of ornithine decarboxylase [DR112(pODC)] or S-adenosylmethionine decarboxylase [DR112(pSAMDC)]. Although DR112(pODC) produced approximately 70 times more ornithine decarboxylase than DR112 did, the amounts of polyamines in the cells of both strains did...

The use of methylglyoxal-bis(guanylhydrazone) (MGBG) in the clinical treatment of myeloid and lymphoid disorders has been limited by severe host toxicity to renewing tissues, particularly the intestinal mucosa. Since the drug is a potent inhibitor of spermidine biosynthesis, the distributions of ornithine and S-adenosylmethionine decarboxylases and polyamine pools have been characterized in the...