Search PubMed⌕ Search

Biomedical subjects

T Lloyd

Publications and source records attributed to T Lloyd.

At least 91 records · Page 5Linked to original sources
PubMed1978

Direct inhibition of tyrosine hydroxylase activity by catechol estrogens.

Catechol estrogens, the 2-hydroxylated metabolites of estrogens, recently shown to be formed in brain, inhibit tyrosine hydroxylase, the enzyme that catalyzes the pivotal step in the biosynthesis of the neurotransmitters dopamine and norepinephrine. The nature of the inhibition is by competition with the pterin cofactor and thus resembles feedback inhibition of the enzyme by catecholamines.

Animals↗
PubMed1978

Methylation of estradiol-17 beta by a partially purified preparation of bovine pineal hydroxy-indole-O-methyltransferase.

A partially purified preparation of hydroxy-indole-O-methyltransferase (HIOMT) from bovine pineal was shown to O-methylate estradiol-17beta (E2). The HIOMT preparation was incubated with E2 and [3H]-S-adenosylmethionine (SAM). The [3H]-3 methyl-ether or estradiol [MeO-E2] produced was identified by thin layer chromatography (TLC) and crystallization to constant 3H/14C ratio in the presence of [14C]-MeO-E2 and unlabeled MeO-E2 standards. The kinetics of the enzyme reaction for melatonin formation from N-acetyl-serotonin (NAS) and for MeO-E2 were compared.

Acetylserotonin O-Methyltransferase↗
PubMed1976

Studies on phenylalanine and tyrosine hydroxylation by rat brain tyrosine hydroxylase.

Tyrosine hydroxylase (EC1.14.16.2), presumably the rate-limiting enzyme in the biosynthesis of catecholamines, is known to catalyze the hydroxylation of both phenylalanine and tyrosine. Using both an isolated enzyme preparation and a synaptosomal preparation, where some architectural integrity of the tissue has been preserved, we have attempted to evaluate the manner in which these two substrates are hydroxylated by rat brain tyrosine hydroxylase. In the presence of tetrahydrobiopterin the isolated enzyme catalyzes the hydroxylation of phenylalanine to 3,4-dihydroxyphenylalanine with the release of free tyrosine as an obligatory intermediate. In contrast, the rat brain striatal synaptosomal preparation in the presence of endogenous cofactor converts phenylalanine to 3,4-dihydroxyphenylalanine without the release of free tyrosine.

Animals↗