Benzoylproteine: Benzoyl-Ovalbumin und dessen Hydrolyse. V. Mitteilung über Proteine.

Abstract

By benzoylating ovalbumin in KHCO3 solution there is formed a benzoyl-ovalbumin containing 17% benzoyl. The total content of benzoyl is determined by benzoylating with chlorbenzoyl chloride and determining the Cl content of the resulting chlor-benzoyl-al-bumins. The authors improved upon the method of Goldschmidt and Schon for the estimation of benzoyl in benzoylated albumins. If the splitting off of benzoyls from benzoyl-albumin is effected by normal NaOH at 100[degree] C. and with 70% H2SO4 at 34[degree] C. or 100[degree] C, one obtains in all 3 cases steplike curves with points of inflection; the benzoyl must therefore exist in at least 3 different combinations. The benzoyl fraction compound which is split off with the greatest difficulty constitutes about 7% of the total and remains unaffected even after treatment with 70% H2SO4 at 100[degree] C., whereas the peptid linkages of the albumin are broken down by this treatment to the individual amino-acids. It was possible to isolate [epsilon]-benzoyl lysin from these split products. From this the authors conclude that a part of the benzoyl which is resistant to cleavage must be linked to the e-amino group of lysin; also that the [epsilon]-amino group of lysin in ovalbumin remains at least in part in the free condition. In view of the fact that the amount of lysin contained in albumin accounts only for 4% of the benzoyl that is linked to the e-amino group; therefore 3 to 4% of the benzoyl which is split off with difficulty must be linked to some other group in the compound.