ANALYSIS OF THE MECHANISM OF CHOLESTEROL SIDE CHAIN CLEAVAGE REACTION AND ITS RELATED HEREDITARY DISEASES

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Steroid hormones play an important role in normal life activity for higher animals, and the disorders of these hormones result in the severe diseases for the animal. The ratelimiting step of steroid hormone biosynthesis is cholesterol side chain cleavage reaction catalyzed by cytochrome P-450scc in mitochondria. Chogenital lipoid adrenal hyperplasia which is called as Prader Syndrome has been believed as a deficiency of cytochrome P-450scc. However, Yasuda, a collabolator of this research has reported that cDNA for cytochrome P-450scc of the patient is not different from that of normal subject, and cytochrome P-450scc protein is actually expressed in the patient testis. Miller and colleagues in US also reported that cDNAs for adrenodoxin reductase (AR) and adrenodoxin (AD) of the patient are not also different from those of normal subject as well as in the case of cDNA for cytochrome P-450scc. From these investigations, the reason why cholesterol side chain cleavage reaction is diminis … More hed in the patient with Prader Syndrome is not yet clear.In this study, we attempted to elucidate the mechanism of decrease in the activity being focused on the interactions among AR,AD,and cytochrome P-450scc using enzymological techniques. Blotting analyzes of AR,AD,and cytochrome P-450scc showed that the contents of these enzyme components in the testis of the patient were not so different from those of normal subject. Cholesterol side chain cleavage activity of the patient testis mitochondria was 35% of that of normal subject indicating that the activity of the patient testis mitochondria is not always zero level. Phospholipid/protein value of the patient testis mitochondria was 0.380 whereas the value of the normal subject was 0.659, indicating that phospholipid of the patient testis mitochondria decreased significantly. We extracted phospholipid from mitochondria of the patient testis and analyzed the content of subclass of phospholipids. We found that the content of lysolecithin in the patient testis mitochondria increased 7-fold of that of normal subject. Lysolecithin is known to inhibit cholesterol side chain cleavage activity in mitochondria. We also confirmed the inhibitory effect of lysolecithin in the reconstituted system using AR,AD,and cytochrome p-450scc purified from bovine adrenal cortex. These results suggest that the increased level of lysolecithin found in testis mitochondria from the patient is related to the mechanism of decrease in the activity in congenital lipoid adrenal hyperplasia. Less