Role of intestinal brush border membrane aminopeptidase N in dipeptide transport

The kinetics of uptake of radioactive label from [U-14C]Gly, L-[4,5-3H]Leu and the dipeptide [14C]Gly-L-[4,5-3H]Leu by the brush border membrane vesicles of porcine small intestine have been studied. The effect of aminopeptidase N inhibitors and leucine-binding protein on accumulation rates has also been tested. Comparison of the kinetic parameters for uptake and hydrolysis of Gly-L-Leu makes it possible to conclude that the dipeptide transfer includes two conjugated steps, viz., hydrolysis catalysed by aminopeptidase N and transport of the resultant free amino acids by a specific carrier.     

H NMR study on the interaction between trans-Cl2Pd(dipeptide)2 (dipeptide is glyglyOH and gly-L-nvalOH) and the dodecanucleotide [d(CGCGAATTCGCG)]2

The metal binding properties of trans-Cl₂Pd(glyglyOH)₂ and trans-Cl₂Pd(glynvalOH)₂ towards the oligonucleotide dodecamer [d(CGCGAATTCGCG)]₂ duplex, have been studied by 1D and 2D ¹H NMR spectroscopy. A selective binding of the metal with G₄, followed by G₂ was observed with both complexes. This indicates that an intrastrand GNG(G₂C₃G₄)(N₇-N₇) chelation of Pd(II) with the dodecamer duplex may have taken place. The Pd(II)-duplex interaction is less aggressive with trans-Cl₂Pd(glynvalOH)₂, than with trans-Cl₂Pd(glyglyOH)₂. NOE connectivities in the first case show a through space hydrophobic ligand–ligand interaction of the dipeptide and oligonucleotide protons.     

The occurence of cystinylglycine in blood plasma

Cystinylglycine has been identified as a minor ninhydrin-positive component of deproteinized blood plasma from human, bovine, rat and rabbit blood. The amount present in human blood plasma is approximately one-fifth of that of cystine and is not significantly correlated with age or with the cystine level.