Relationship of amino acid composition and molecular weight of antifreeze glycopeptides to non-colligative freezing point depression

Joseph D. Schrag, Scott M. O'Grady, Arthur L. Devries

Research output: Contribution to journalArticle

Abstract

Many polar fishes synthesize a group of eight glycopeptides that exhibit a non-colligative lowering of the freezing point of water. These glycopeptides range in molecular weight between 2600 and 33700. The largest glycopeptides [1-5] lower the freezing point more than the small ones on a weight basis and contain only two amino acids, alanine and threonine, with the disaccharide galactose-N-acetyl-galactosamine attached to threonine. The smaller glycopeptides, 6, 7, and 8, also lower the freezing point and contain proline, which periodically substitutes for alanine. Glycopeptides with similar antifreeze properties isolated from the saffron cod and the Atlantic tomcod contain an additional amino acid, arginine, which substitutes for threonine in glycopeptide 6. In this study we address the question of whether differences in amino acid composition or molecular weight between large and small glycopeptides are responsible for the reduced freezing point depressing capability of the low molecular weight glycopeptides. The results indicate that the degree of amino acid substitutions that occur in glycopeptides 6-8 do not have a significant effect on the unusual freezing point lowering and that the observed decrease in freezing point depression with smaller glycopeptides can be accounted for on the basis of molecular weight.

Original languageEnglish (US)
Pages (from-to)322-326
Number of pages5
JournalBBA - General Subjects
Volume717
Issue number2
DOIs
StatePublished - Aug 6 1982

Keywords

  • Amino acid composition
  • Antifreeze glycopeptide
  • Freezing point depression
  • Glycopeptide
  • Molecular weight

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Molecular Biology

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