The assimilation of amino acids by bacteria. 27. The relationship between glycerol and ‘incorporation factor’

Abstract

The incorporation of glycine into TCA-precipitable fraction of Escherichia coli KI, harvested in the early exponential stage of growth and preincubated for 30 min. in buffered saline, is stimulated 10- to 13-fold by incorporation factor'' preparation. The response is linear with time for at least 2 hr. Glycerol has little or no initial effect under these conditions, but stimulation develops during incubation and after a lag period of about 60 min. An initial concentration of 0.1 m[image] -glycerol gives a stimulation equivalent to that obtained with incorporation factor. Higher concentrations of glycerol are not more effective. When the washed cells are incubated with glycerol for 60 min. before the addition of glycine, incorporation of the latter is stimulated immediately on addition and the response is linear. Glucose gives an immediate stimulation of glycine incorporation but the effect decreases rapidly with time. No breakdown product of glycerol has been found which has significant stimulatory action. A ''formin'' preparation containing formic acid esters of glycerol is approximately 3 times as active as glycerol itself. Other glycerides are inactive. Glycerol is markedly less effective than incorporation-factor preparation in promoting glutamic acid incorporation, under conditions of protein synthesis, in disrutped staphylococcal cells. Formin is again more effective than glycerol; and, at a relatively high concentration, it can replace the incorporation-factor preparation.