Comparison of Characteristics of Hepatic Microsomal Cytochrome P45O-dependent Monooxygenases from Snake and Rat

꽃뱀과 흰쥐의 간 마이크로좀에 존재하는 Cytochrome P45O 의존성 Monooxygenases의 특성 비교

This study was carried out to investigate levels of the components of microsomal mixed function oxidase (MFO) system and activities of the hepatic microsomal cytochrome P45O (P45O)-dependent monooxygenases of grass snake (Natrix tigrina Lateralis) and to compare with those of rat. The levels of P45O and cytochrome b$_{5}$, (b$_{5}$) of snake were much lower than those in rat. NADPH-cytochrome c reductase activity in the snake was also only 40% of that in the rat. Activities of 7-ethoxycoumarin 0-deethylase (ECOD) and benzphetamine N-demethylase (BPDM) of snake hepatic microsomes, when compared with those of rat, were markedly low. But, aryl hydrocarbon hydroxylase (AHH) and testosterone hydroxylase (TSH) activities were nearly the same or higher than those of the rat. Of the P45O-dependent TSHs measured, 7$\alpha$-hydroxylase activity was the highest in snake, whereas, 6$\beta$-hydroxylase activity was the highest in rat. However, stereoselectivity of the enzyme from the snake to C2 and C6 positions of testoste-rone was the same as rat. The result of radioimmunoassay (RIA) for the identification of five P45O isozymes with MAbs shows that relatively high content of ethanol-inducible P45O isozyme, CYP2El, exists in the rat, whereas MC-inducible P45O isozyme, CYP2A1/1A2, does in the snake. From the analyses of SDS-PAGE and RIA of partially pu-rified P45O, we suggest the possibility of the presence of a certain P45O isozyme(s) in hepatic microsomes of snake different from those of rat.

한국산 꽃뱀(Natrix tigrina Lateralis)의 간 마이크로좀에 존재하는 mixed function oxidase system 구성 성분들의 함량과 P45O 의존성 monooxygenase의 활성도를 조사하고 이들을 흰쥐(Sp. D)의 것과 상호 비교하였다. 꽃뱀에서의 P45O, b5 함량 및 NADPH-cytochrome c reductase 활성도는 흰쥐에서 보다 낮았으며, 7-ethoxycoumarin O-deethylase와 benzphetamine N-demethylase 활성도 역시 흰쥐에서 보다 상당히 낮았다. 그러나 aryl hydrocarbon hydroxylase와 testosterone hydroxylase 활성도는 흰쥐와 비교할 때 거의 비슷하거나 오히려 높았다. Testosterone의 수산화 반응에 대한 선택특이성을 조사한 결과, 꽃 뱀은 7$\alpha$ 위치에서, 흰쥐는 6$\beta$ 위치에서 가장 높은 수산화 반응물을 생성했다. 그러나 testosterone의 C2와 C3 위치에서의 수산화 반응에 대한 선택특이성은 꽃뱀과 흰쥐에서 비슷하였다. Radioimmunoassay (RlA)를 실시하여 5종 (CYP2B, CYP1A1, CYP1A2, CYP3A 및 CYP2El)의 P45O 동위효소의 구성비를 비교한 결과, 꽃뱀에서는 CYP1A1/1A2가, 흰쥐에서는 CYP2El이 각각 비교적 많이 존재하였다. 부분정제한 P45O을 SDS-PAGE와 RIA로 분석한 결과, 꽃뱀의 간 마이크로좀에 존재하는 P45O중에는 흰쥐와는 다른 종류의 P45O 동위효소가 존재함을 시사하였다.