Other Proteins Reported To Have Antifreeze Activity

Other Proteins Reported To Have Antifreeze Activity 

Although the families of the Antarctic fish and the northern cod (No-totheniidae and Gadidae, respectively) are widely separated, their AFGP have been found to be very similar. 

The polar cod frequents the far north Atlantic Ocean, the Barents Sea, and the Arctic Ocean, and, as such, and as its name implies, it is truly a polar fish. It is not surprising then that, when four species of fish were caught in the Barents Sea with temperatures varying from - 1.2°C to — 1.3°C at 79° N and 10-40 miles south of the southern end of a loose ice pack (frequent, but separated, small icebergs), only the polar cod was found to contain an antifreeze protein (Osuga and Feeney, 1978). This area would represent the near northern latitudes where the other three fish would go at that time and ocean temperature, while the polar cod is also found in more northern waters. 

Initial studies on the polar cod blood serum have shown that its antifreeze protein is a glycoprotein with most properties similar to those from the Antarctic species T. borchgrevinki. Both active and inactive components were obtained. The active components had the same ratios of alanine to threonine (approximately 2 1) as found in the Antarctic glycoproteins and the same contents of galactosamine and galactose. No other amino acids were found. In contrast to the comparatively low antifreeze activity of the saffron cod reported by Raymond and co-workers, the AFGP from the polar cod had an antifreeze activity similar to that from the Antarctic species. 

The active and inactive components were also found to be in approximately the same relative amounts as the Antarctic ones. The smaller inactive component number 8 had the same relative amino acid contents, which included, of course, the presence of proline in the approximate ratio for alanine threonine proline of 4 2 1. This similarity in composition explains the identical electrophoretic migra- 

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VII. Other Proteins Reported To Have Antifreeze Activity. 246... 

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