The tripeptide title compound, C(32)H(53)N(3)O(6), synthesized in 80% yield by coupling of N-methyl-l-leucine benzyl ester with tert-butoxy-carbonyl-l-leucyl-N-methyl-l-leucine at 273 K, conjugates through two amide linkages and includes two protecting groups: a tert-butyl-oxycarbonyl group at the C-tip and a benzyl group at the N-tip. A classical inter-molecular N-H⋯O hydrogen bond and a weak ...

Pseudorevertants able to use L-leucyl-L-leucyl-L-leucine as a leucine source have been isolated from a Salmonella typhimurium strain carrying stable (nonreverting) mutations in pepN, pepA, and pepB. These strains carry mutations at a locus pto (peptidase T overproducer) tightly linked to pepT that cause an elevated expression of the tripeptidase peptidase T. An F' episome carrying the pto and p...

Cytotoxicity of melphalan to murine L1210 leukemia cells was reduced to a limiting maximum value of 50% by 2-aminobicyclo[2,2,1]heptane-2-carboxylic acid (BCH), indicating that cytotoxicity is partially dependent on drug uptake by system L. L-Leucine, but not alpha-aminoisobutyric acid (AIB), completely reduced the remaining 50% of drug cytotoxicity. These results contrast with those obtained w...

The present work aims to develop a growth medium to render a wild-type strain of Saccharomyces cerevisiae permeable to the antifungal drug Brefeldin A. In the current study, a synthetic medium containing 0.1% L-proline and supplemented with $3.0\times 10;{-3}$ % SDS is employed. When Brefeldin A is added to this medium, a wild-type strain shows increased growth sensitivity and a diminished tran...

We investigated the impact of growth hormone (GH) alone, testosterone (T) alone, and combined GH and T on whole body protein metabolism. Twelve hypopituitary men participated in two studies. Study 1 compared the effects of GH alone with GH plus T, and study 2 compared the effects of T alone with GH plus T. IGF-I, resting energy expenditure (REE), and fat oxidation (F(ox)) and rates of whole bod...

Leucine and leptin play important roles in regulating protein synthesis and degradation in skeletal muscles in vitro and in vivo. However, the objective of the present study was to determine whether leptin and leucine function synergistically in regulating protein metabolism of skeletal muscles. In the in vitro experiment, C2C12 myotubes were cultured for 2 h in the presence of 5 mm-leucine and...

Cancer patients present high mobilization of host protein, with a decrease in lean body mass and body fat depletion occurring in parallel to neoplastic growth. Since leucine is one of the principal amino acids used by skeletal muscle for energy, we investigated the changes in body composition of pregnant tumor-bearing rats after a leucine-supplemented diet. Sixty pregnant Wistar rats divided in...

Uptake of L-[H]leucine by lobster hepatopancreatic brush-border membrane vesicles was stimulated by a transmembrane NaCl gradient (o>i ) , but not by identical gradients of NaSCN or other Cl~ salts (e.g. K, Li, NH4 , Cs or choline), suggesting that amino acid transfer depended upon both Na and Cl~. In NaCl medium at acidic pH, leucine uptake was largely electroneutral and unresponsive to a tran...

BACKGROUND & AIMS The reference method to study protein and arginine metabolism in critically ill children is measuring plasma amino acid appearances with stable isotopes during a short (4-8 h) time period and extrapolate results to 24-h. However, 24-h measurements may be variable due to critical illness related factors and a circadian rhythm could be present. Since only short duration stable i...