Enzyme kinetics in mammalian cells. I. Rate constants for galactose metabolism in erythrocytes of normal galactosemic, and heterozygous subjects.

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Abstract
Red cell lysates quantitatively obey expected theoretical relationships governing the rate of the first steps of galactose metabolism. A simple and reproducible determination of cellular rate constants is possible. The rate constant for the 2nd step in the reaction chain is normally 10 times that of the 1st, a situation which would preclude accumulation of the toxic intermediate, galactose-1-phosphate. The rate constants for the kinase enzyme were the same for red cells from normal, galactosemic, and heterozygous subjects, and from whole and lysed cells. The transferase enzyme obeys a simple, gene-dosage relationship. The methodology appears useful for study of gene-enzyme relationships and regulatory processes in metabolic chains from different types of mammalian cells, and for heterozygote screening in large populations.