No abstract

For the first time, in vivo utilization of two highly soluble and stable cystine-containing synthetic short-chain peptides, bis-L-alanyl-L-cystine and bis-glycyl-L-cystine, were investigated in adult rats. Within 5 min after an intravenous bolus, blood samples were drawn (inferior vena cava) and plasma amino acid and peptide levels were determined using RP-HPLC (precolumn derivatization with 5-dimethylaminonaphthalene-1-sulfonylchloride). Both peptides were rapidly cleared from plasma (estimated elimination t1/2: 4 min for the glycyl peptide and less than 2 min for the alanyl peptide). The initial high amounts of mono-L-alanyl-L-cystine and mono-glycyl-L-cystine as well as the prompt increase of the constituent free amino acids alanine, glycine and cystine strongly suggest that the peptide disappearance is mainly due to a very fast two-step hydrolysis in the extracellular compartment, presumably catalyzed by soluble and/or plasma membrane-bound peptidases. The observed rapid hydrolysis may serve as first evidence that short-chain peptides with C-terminal cystine residue may represent efficient sources of free cystine in parenteral nutrition.

For the first time, in vivo utilization of two highly soluble and stable cystine containing synthetic short chain peptides, N,N'-bis-L-alanyl-L,L-cystine and N,N'-bis-glycyl-L,L-cystine, was investigated in adult rats. Within 5 min after an intravenous bolus, blood samples were drawn (inferior vena cava) and plasma amino acid and peptide levels were determined using RP-HPLC (precolumn derivatization with 1-dimethylaminonaphthalene-5-sulfonylchloride). Both peptides were rapidly cleared from plasma (estimated elimination time: 4 min for the glycyl peptide and less than 2 min for the alanyl peptide). The initial high amounts of N-L-alanyl-L,L-cystine and N-glycyl-L,L-cystine as well as the prompt increase of the constituent free amino acids alanine, glycine and cystine strongly suggest that the peptide disappearance is mainly due to a very fast two-step hydrolysis in the extracellular compartment, presumably catalyzed by soluble and/or plasma membrane bound peptidases. The observed rapid hydrolysis may serve as first evidence that short chain peptides with C-terminal cystine residue may represent efficient sources of free cystine in parenteral nutrition.