In recent years, a great deal of evidence has accumulated indicating that carbohydrate metabolism involves phosphorylated intermediaries (see reviews of Lipmann, '41 ; Kalcker, '42; and Cori, '42). Most of this evidence has been adduced from the study of tissue extracts and relatively simple sys- tpms of enzymes and substrates. Phosphorylation in intact cells is more difficult to demonstrate because steady states may exist whereby phosphorylated compounds are decomposed almost as rapidly as they are synthesized, with little net change in concentration.
Changes in the concentrations of various phosphate fractions have been demonstrated in the living yeast cells, during anaerobic metabolism of sugar (Levitov, '36; Ostern et al., '38 ; Kruyk and Klingmuller, '39 ; I\lcFar.lane, '39 ; and bIirslci and Wertheimer, '39).
I n this paper further evidence will be presented concerning the relationship of phosphorylation to carbohydrate metabolism in the living yeast cell, with special reference to aerobic metabolism. METHODS Fresh Baker's yeast (Standard Brands Inc.) was used for all experiments. The yeast was washed twice and suspended in the experimental medium. During washing, the centrifugal Present Address : Biochemistry and Pharmacology Department, School of Mectirinr and Dentistry, T!niversit>7 of Rochester, Rochester, N. Y.