These studies will continue to study the genetics of human proteins using cell culture techniques. The major approaches used are those of gene mapping through cell hybridization and the analysis of the rates of synthesis and degradation of individual proteins. We are currently in the process of mapping the human and mouse loci responsible for the structural determinants of UDP-galactose epimerase (GALE) and catalase. In these experiments human-mouse hybrids segregating either mouse or human chromosomes are being studied. Having demonstrated that N-bromoacetyl-B-D-galactosylamine inhibits the expression of a number of lysosomal enzymes including Beta-galactosidase, we have demonstrated that there is an affect on the total amount of cell protein. This inhibitor appears to be a reversible one and therefore may be useful for analyzing the turnover of proteins in human cells. With the use of specific immuno-absorbent, we are actively pursuing the measurement of turnover of human galactose-1-phosphate uridylyltransferase in normal and mutant human cells. BIBLIOGRAPHIC REFERENCES: Chern, C.J., Mellman, W.J. and Croce, C.M. Assignment of the gene for cytoplasmic glutamic-oxaloacetic transaminase to the region q24-qter of human chromosome 10. Somatic Cell Genetics 2: 177, 1976. Greenstein, M. and Mellman, W.J. Influence of serum concentration and insulin upon catalase levels in normal human diploid fibroblasts. (Abstract). Ann. Meeting Am. Soc. Microbiol., 1977.