Tracer studies with avocado tissues indicate that methionine is converted to ethylene at stages of the climacteric rise and the climacteric peak, but not at the preclimacteric stage. The results suggest that the control of ethylene biosynthesis is at a step after methionine is synthesized. The endogenous content of methionine was found to be so low that methionine must be actively turned over f...

The unambiguous study of homocysteine metabolism requires a source of [355]homocysteine completely free from contaminating [35S]methionine. Until now, such a reagent has not been readily available. Homocysteine is an important metabolite involved in methionine, cysteine and methylation metabolism. Homocysteine can be methylated to form methionine with either 5-methyltetrahydrofolate [1] or beta...

1. Antioxidant and methyl donor effects of betaine in experimental animal models have recently been demonstrated. The present study was therefore designed to examine the antioxidant effects of betaine on the antioxidant status and meat quality of breast muscles in broilers. 2. Cobb broilers were randomly divided into Control, Methionine low, Methionine low plus betaine, and Betaine groups. 3. T...

Multicopper oxidases are widely studied enzymes catalyzing the oxygen reduction reaction. Among this family, one class belongs to copper efflux oxidases. They far less in bioelectrochemistry mainly because of low potential at which they reduce O2. However, presence a specific domain rich methionine residues covering first electron acceptor induces fundamental issues regarding transfer pathway. ...

Background/Aim: Methionine addiction is a general and fundamental hallmark of cancer due to the excess use methionine for transmethylation reactions, termed “Hoffman Effect”. has been shown be highly-effective target therapy by restriction with oral recombinant methioninase (o-rMETase) in preclinical studies, including patient- derived orthotopic xenograft (PDOX) mouse models cancer. A clinical...

The effect of methylcobalamin inactivation by the gas nitrous oxide on plasma amino acid and tissue methionine levels in fruit bats (Rousettus aegyptiacus) was examined. Animals exposed to N2O-oxygen (1:1, v/v) for 90 min daily received a fruit diet with or without methionine or betaine supplements. Exposure and diets were continued for up to 17 weeks or until neurological impairment and muscul...

We investigated sulfur and methyl group metabolism in a 31-yr-old man with partial hepatic methionine adenosyltransferase (MAT) deficiency. The patient's cultured fibroblasts and erythrocytes had normal MAT activity. Hepatic S-adenosylmethionine (SAM) was slightly decreased. This clinically normal individual lives with a 20-30-fold elevation of plasma methionine (0.72 mM). He excretes in his ur...

Methionine is a protective factor against various types of liver damage, but excessive dietary methionine is hepatotoxic. Because the mechanisms of L-methionine-related hepatotoxicity are poorly understood, the effect of long-term excessive L-methionine intake on the metabolism of iron and antioxidants was studied in rat liver to determine whether oxidative stress is involved. Wistar male rats ...

Although the importance of methyl metabolism in fetal development is well recognized, there is limited information on the dynamics of methionine flow through maternal and fetal tissues and on how this is related to circulating total homocysteine concentrations. Rates of homocysteine remethylation in maternal and fetal tissues on days 11, 19, and 21 of gestation were measured in pregnant rats fe...

Cobalamin-independent methionine synthase (MetE) catalyzes the final step in Escherichia coli methionine biosynthesis but is inactivated under oxidative conditions, triggering a methionine deficiency. This study demonstrates that the mutation of MetE cysteine 645 to alanine completely eliminates the methionine auxotrophy imposed by diamide treatment, suggesting that modulation of MetE activity ...