The relationship between molecular weight and antifreeze polypeptide activity in marine fish

Abstract

Previous studies have established that the capacity of the glycopeptide antifreezes to depress the freezing temperature of aqueous solutions is positively correlated with molecular weight. The present study was carried out to determine whether a similar correlation existed within the antifreeze peptides. Two approaches were used. Initially, the antifreeze activity (thermal hysteresis) curves of antifreeze peptides from winter flounder, Pseudopleuronectes americanus (molecular weight, 3300), shorthorn sculpin, Myoxocephalus scorpius (molecular weight, 4000), ocean pout, Macrozoarces americanus (molecular weight, 6000), and sea raven, Hemitripterus americanus (molecular weight, 9700), were compared. In the second approach, a more specific comparison was made of two different sized antifreeze peptide components (molecular weights, 2900 and 4000) from the shorthorn sculpin. In both approaches, antifreeze peptide activity was positively correlated with molecular weight and the curve illustrating this relationship suggests that any reduction in molecular weight below 3300 will result in a disproportionate decline in activity. The relatively small antifreeze peptides from the winter flounder and shorthorn sculpin had greater activity than did glycopeptide antifreezes of similar size. However, glycopeptide antifreezes with a molecular weight of 10 000 or more had activities that exceeded that of any known antifreeze peptide. Increases in molecular weight of antifreeze peptides above 4000 resulted in a decline in antifreeze activity per milligram protein. Therefore, in terms of ability to depress the freezing temperature, there appears to be no advantage in evolving large antifreeze peptide molecules.

Ca2+-dependent Antifreeze Proteins

“…Activity measurement requires very high concentrations of AFP. In addition, the activity of fish AFPs increases in a nonlinear fashion with protein concentration forming a hyperbolic curve (Kao et al, 1986). This study does, however, provide a clear illustration of the metal ion requirements of the AFP when present at physiological concentrations in herring blood.…”

Antifreeze activity in the gastrointestinal fluids ofArctogadus glacialis(Peters 1874) is dependent on food type

“…The polyacrylamide gel electrophoresis showed that the AFGPs are degraded into many sub-sizes during the digestion process. As pointed out in other studies, the size composition of AFGP have crucial influence on the antifreeze activity (Ahlgren and DeVries, 1984;Kao et al, 1986;Osuga et al, 1978;Schrag et al, 1982). Thus, a possible explanation for the high antifreeze activity can be the combination of many sub-sizes of AFGP and the fact that the concentration of AFGP increases in the intestine due to water uptake by the gut wall (O'Grady et al, 1982b).…”

“…The AFGPs appear in at least eight sizes with molecular masses ranging between 2.6-33.7·kDa, but recent high resolution gradient gels show at least 15 molecular isoforms (Chen et al, 1997). The ) have the greatest antifreeze activity (Kao et al, 1986;Osuga et al, 1978;Schrag et al, 1982), whereas the smaller AFGP6-8 (7.9-2.6·kDa) only exhibit up to a third of the antifreeze activity of AFGP1-5 (Kao et al, 1986;Osuga et al, 1978;Schrag et al, 1982). Furthermore, it has been shown that the antifreeze activity strongly depends on the AFGP concentration (O'Grady et al, 1982a).…”

Structural variations in the alanine‐rich antifreeze proteins of the pleuronectinae

“…The partially purified AFP were resolved into individual components by reversephase high-performance liquid chromatography (HPLC) using a Waters pBondapak CIS column (0.78 x 30 cm) with an acetonitrile gradient in 0.05% trifluoroacetic acid. Antifreeze activity of the components, as determined by thermal hysteresis values [17], was measured by a nanolitre osmometer (Clifton Technical Physics, Hartford, NY, USA).…”