Regulation of galactose-1-phosphate uridyltransferase gene expression

Analysis of both the human and rat galactose-1-phosphate uridyltransferase (GALT) genes reveal 5' regulatory consensus sequences suggestive of a housekeeping gene. This is in accord with the finding of GALT activity in all tissues. However, the complications seen in galactosemia, in particular ovarian dysfunction and verbal dyspraxia, suggest organ-specific sensitivity to lack of GALT activity. Analysis of steady-state GALT mRNA and specific activity levels in adult rat organs reveals a marked difference between organs that correlates with the degree of organ dysfunction in humans with galactosemia. The organ variation in GALT mRNA and activity thus appears to be due to genetic regulation. Discernment of the pathophysiologic basis for the organ-specific complications requires an understanding of the basis for the differences in organ regulation. The present state of knowledge of the regulation of the Leloir enzymes in general, GALT in particular, from prokaryotes to mammals is discussed.