ChemInform Abstract: CARBOXYL-TERMINAL AMINO ACID RESIDUE ANALYSIS OF PEPTIDES, A NEW METHOD

1975 ◽  
Vol 6 (46) ◽  
pp. no-no
Author(s):  
MARVIN J. MILLER ◽  
GORDON MARC LOUDON
Keyword(s):  
Amino Acid ◽  
Amino Acid Residue ◽  
Residue Analysis ◽  
New Method ◽  
Terminal Amino Acid ◽  
Terminal Amino ◽  
Carboxyl Terminal

Plasma Oxytocinase: The Synthesis and Biological Properties of the First Prodoct of the Degradation of Oxytocin by this Enzyme

1974 ◽  
Vol 52 (1) ◽  
pp. 60-66 ◽  
Author(s):  
B. M. Ferrier ◽  
J. M. Hendrie ◽  
L. A. Branda
Keyword(s):  
Amino Acid ◽  
Substrate Specificity ◽  
Pregnant Women ◽  
Amino Acid Residue ◽  
Biological Properties ◽  
Milk Ejection ◽  
Terminal Amino Acid ◽  
Molecular Features ◽  
Marked Inhibition ◽  
Terminal Amino

Oxytocin is hydrolytically cleaved in the presence of plasma oxytocinase to give an acyclic peptide, tyrosyl-isoleucyl-glutaminyl-asparaginyl-S-(S-cysteine)-cysteinyl-prolyl-leucyl-glycinamide (1,2-acyclic oxytocin). The synthesis of this peptide is described. It is shown to be of very low potency in milk-ejection-like activity and uterotonic activity. It does not inhibit the expression of these activities by oxytocin, suggesting that it does not interfere with the hormone's binding to target tissues. The presence of 1,2-acyclic oxytocin slightly inhibits the rate of degradation of oxytocin by plasma from pregnant women, in contrast to the marked inhibition of the degradation of cystine di-β-naphthylamide. The Km for the degradation of oxytocin is 30 times smaller than that of the degradation of cystine di-β-naphthylamide, which is of the same order as the Ki for the inhibition of the degradation of cystine di-β-naphthylamide by 1,2-acyclic oxytocin. These results, together with information on the substrate specificity of plasma oxytocinase with respect to the N-terminal amino acid residue, suggest that there are molecular features of oxytocin other than its N-terminal residue that facilitate its interaction with plasma oxytocinase.

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