Protein of Fruits

Abstract

IN continuation of the work on apple-fruit protein, it has been found that if, after the initial treatment of the frozen and ground tissue with alkaline buffers¹, extraction with this buffer is prolonged for several hours at 1° C. and the tissue is then washed with a small quantity of the buffer, the combined extract and washings may contain as much as 85 per cent of the original protein. A much larger proportion of non-nitrogenous material is also dispersed into the solution, with the result that when precipitation of the protein-complex is caused by adjustment of the pH. to 6, the nitrogen content of the precipit ite is only 5 per cent. At pH less than 4 or, if precipitation is brought about by treatment with ammonium sulphate (to half-saturation), the nitrogen content falls as low as 4 per cent. Of great interest is the fact that the ammonium sulphate precipitates are partially soluble in water or phosphate buffer of pH. 8; and the resultant solutions, after dialysis at 1° C., show a positive oxidase action, a strong peroxidase action and a small but definite amylase action (greatly reduced, no doubt, by the presence of tannin). Acid precipitates, however, even after precipitation at low temperatures, are practically insoluble in water and exhibit none of the above enzyme activity.