Gastrointestinal (GI) tract leucine metabolism was measured in 6- to 9-mo-old lambs subjected to trickle infection with Trichostrongylus colubriformis larvae and in separate animals that were not infected. Animals prepared with a jejunal catheter and with indwelling catheters into the aorta and the portal- (PDV) and mesenteric- (MDV) drained viscera were infused simultaneously with [1-13C] and ...

5',5',5'-Trifluoro-dl-leucine inhibited the activity of alpha-isopropylmalate synthetase (the initial enzyme unique to leucine biosynthesis) as well as the growth of Salmonella typhimurium. Mutants of S. typhimurium resistant to the analogue were isolated and characterized. In most cases, they overproduced and excreted leucine or leucine, valine, and isoleucine as a result of an alteration in t...

Several studies showed that l-leucine supplementation reduces adiposity when provided before the onset of obesity. We studied rats that were exposed to a high-fat diet (HFD) for 10 weeks before they started to receive l-leucine supplementation. Fat mass was increased in l-leucine-supplemented rats consuming the HFD. Accordingly, l-leucine produced a hypothalamic pattern of gene expression that ...

The postprandial increases in AA and insulin independently stimulate protein synthesis in skeletal muscle of piglets. Leucine is an important mediator of the response to AA. We have shown that the postprandial increase in leucine, but not isoleucine or valine, acutely stimulates muscle protein synthesis in piglets. Leucine increases muscle protein synthesis by modulating the activation of mamma...

The leucine zipper is the dimerization domain of the B-ZIP (basic-region leucine zipper) class of eukaryotic transcription factors (Vinson et al., 1989). The name arose because leucines occur every seven amino acids in this dimerization domain.These leucines are critical for the dimerization and DNA binding of B-ZIP proteins. The leucine zipper is a left-handed parallel dimeric coiled-coil, a s...

There have been many published accounts of idiopathic leucine-sensitive hypoglycaemia of infancy since its description by Cochrane, Payne, Simpkiss, and Woolf in 1956, and raised plasmainsulin levels after the administration of L-leucine have been found in children with this condition (DiGeorge, Auerbach, and Mabry, 1960; Grumbach and Kaplan, 1960; Harmer and Sinclair, 1964). Similar changes in...

An enzyme which condenses acetyl-L-leucyl-L-leucine and L-arginine into acetyl-L-leucyl-L-leucyl-L-leucyl-L-arginine (leupeptin acid) was partially purified from a cell extract of Streptomyces roseus MA839-A1. With respect to this catalytic activity, the enzyme showed the following characteristics: ATP is essential; optimum pH is 9.5; the activity is inhibited either by EDTA or pyrophosphate or...

UNLABELLED l-Leucine was administered as a primed continuous 3-4-h infusion in nonobese and obese subjects in the postabsorptive state and for 12 h in obese subjects after a 3-day and 4-wk fast. In nonobese and obese subjects studied in the post-absorptive state, the leucine infusion resulted in a 150-200% rise in plasma leucine above preinfusion levels, a small decrease in plasma glucose, and ...

Although amino acid mixtures enriched in branched-chain amino acids (BCAA) and deficient in aromatic amino acids (AAA) are often used together with insulin and glucose in clinical nutrition, their physiological effects on muscle protein anabolism are not known. To this aim, we studied forearm leucine kinetics in post-absorptive volunteers, before and after the systemic infusion of BCAA-enriched...