Long-chain Peptides Research Articles

The enzymic hydroxylation of protocollagen models

1. Synthetic polymers of l-prolyl-l-prolylglycine of defined chain length, (Pro-Pro-Gly)(n), were found to be substrates for the enzyme protocollagen-proline hydroxylase, with optimum chain length n=5. Boiling the polymer (Pro-Pro-Gly)(15) increased its activity as a substrate but had no effect on (Pro-Pro-Gly)(5). 2. Protection of both or one of the N- and C-terminal groups made (Pro-Pro-Gly)(3) a better substrate, and collagenase digestion of hydroxylated tert.-pentyloxy-carbonyl-(Pro-Pro-Gly)(3) benzyl ester indicated that the central prolyl residues were the major points of hydroxylation. 3. The results suggest that the long-chain peptides are optimum substrates but that a triple-stranded structure is inhibitory for hydroxylation.

Fraktionierung hydroxyprolin-haltiger harnpeptide mittels sephadex-gelfiltration

Fractionation of Hydroxyproline-containing Urinary Peptides by Sephadex Gel Filtration Concentrated urine samples from 11 healthy persons and from 29 persons with disorders of connective tissue, skin or bone, as well as urine samples from 10 rats, 5 of them lathyritic, were examined. The samples were fractionated by means of gel filtration on Sephadex G-25- The peptide-bound hydroxyproline was determined in the fractions. 25% of hydroxyproline in man and 20% of that in rats was excreted as part of long-chain peptides. We could find no significant variation from this relation in disorders with alteration of the collagen metabolism. We estimated the molecular weights of the long-chain peptides at 1000–6500. The significance of these findings is discussed with reference to the degradation of collagen.

Recent Investigations on the Chemical Nature of Thromboplastin (“TP”) from Human Brain

SummaryIt was confirmed that purified thromboplastin from human brain tissue contains about 18 amino acids after hydrolysis.The following observations gave rise to a discussion if these amino acids are to be considered as contaminations only, or if they derived from a protein moiety of brain thromboplastin.The amino acids are present in all fractions of the thromboplastin and in the wash solutions, and their amount is very small.The amino acids cannot be removed from thromboplastin with the usual techniques, but amino acids and peptides added on purpose can be separated again.Investigations with DNFB pointed to the presence of a great number of precipitable small peptides of various composition. The possibility of the presence of a microamount of a long-chain peptide, or even a trace of protein could not be excluded.Four techniques to separate the amino acid-rich fraction of thromboplastin were studied, described, and the results obtained compared. Sephadex G-25 was most successful, and the fractions were analysed.Most striking was the percentage of aspartic acid in the non-lipid fraction, which is 13-26 times lower than that of proteins and lipoproteins.The biological investigations of these fractions are subject of the subsequent paper.

Primary structure of insoluble tendon collagen: I. N- and C-terminal positional analysis of collagenolytic breakdown products of native collagen

Purified insoluble native Achilles tendon collagen was digested with Clostridium histolyticum collagenase. The N-terminal sequence of the mixed peptides to position 3 was determined by a modification of the Edman degradation procedure, C-terminal amino acids by hydrazinolysis. Experimental losses and non-specific cleavage of the peptides were estimated from model compounds and appropriate corrections made. At the N-terminus 182 residues out of 200 were glycine, 10 were alanine, while isoleucine, phenylalanine, and valine accounted for the remainder. In the second position 77 residues out of 200 were proline, but significant amounts of other amino acids were present showing that the specificity requirement of the enzyme is less rigorous than originally suspected. Ten residues of hydroxyproline in this position were unexpected. In the third N-terminal position the distribution was even more heterogenous, but hydroxyproline and alanine, mostly in tripeptides, predominated. C-terminally, 58 residues were hydroxyproline, 42 alanine, 29 arginine, with other amino acids in considerably lower amounts. No glycine was detected at the C-terminus. Attempts were made to deduce the distribution of third position residues between tripeptides and longer chain peptides and comparisons made with results obtained by others with different collagens.