The Influence of Amino Acids on the Reactivation of Yeast Invertase

Abstract

In a previous paper (1), the influence of some fifteen proteins on the reactivation of yeast invertase was described. Since certain proteins of a nonenzymatic nature partially inhibited the reactivation, it appeared interesting to study the effect of amino acids on the reactivation.The experimental details used in this investigation were the same as those previously described, except that the stock solution of each enzyme preparation was made up so that the phosphate-citrate buffer concentration was 0.2 ~, instead of 0.015 ~r.Three preparations which represent extremes in the degree of purification of invertase were used. These were (1) a commercial preparation sold under the trade name of convertit, a product of the Wallerstein Co., of New York, which contains relatively larger amounts of extraneous material than the other preparations, (2) RNaDKD, and (3) a highly purified preparation RlaDKDA-(S)DAD (preparations 2 and 3 having been made according to the method of Lutz and Nelson (2)). The symbols represent the following: R ---brewery yeast obtained through the kindness of Jacob Ruppert Brewery, N. Y., RI --dilute acid autolysis of brewery yeast (2), RN = neutral autolysis (2), a = alcohol precipitation, D = 24 to 48 hour dialysis, K ----kaolin adsorption, (S) = soluble after saturating with ammonium sulfate (2), A = alumina adsorption.Since the quantity of preparation 3 on hand was limited, most experiments (unless otherwise indicated) were carried out at least in duplicate using preparations 1 and 2. Each result in the following section is therefore an average of 4 determinations. Before reactivation experiments can be done, it is necessary to determine the optimum pH of reactivation for each preparation, and to adjust the alkali for reactivation to obtain this pH because at this point minimum change in velocity occurs with slight change in pH. Effect of Compounds not Containing Stl or S-S GroupsFor these experiments the initial invertase strength was diluted to give a reactivation velocity of from 0.03°/minute to 0.07°/minute. 10 mg. of the compound was used in each experiment. (The reason for using this quantity will be given in a later section.) Accelerations or inhibitions up to 10 per cent 479