Differential expression of succinyl CoA transferase (SCOT) genes in somatic and germline cells of the mouse testis.

Succinyl CoA:3-oxo acid CoA transferase (SCOT/OXCT; EC 2.8.3.5) is a key mitochondrial enzyme in the metabolism of ketone bodies in various organs (but not in the liver). We identified a cDNA clone of the testicular germ cell-specific succinyl CoA transferase isozyme (SCOT-t). We then isolated a mouse orthologue of the SCOT/OXCT cDNA (SCOT-s) and determined the expression of the two types of SCOT in the testis. The mRNAs of scot-s and scot-t were expressed exclusively in testicular somatic cells (i.e. Leydig and Sertoli cells) and germ cells, respectively. SCOT enzymatic activities were assayed in Leydig cell (SCOT-s) and sperm (SCOT-t) fractions. The SCOT activity in sperm was 2.5-fold higher than that in Leydig cells. We conclude that germ cells and somatic cells differentially express the SCOT enzymes and that the SCOT activity of sperm caused exclusively by SCOT-t should play an important role in sperm activity.