추에서 항균 phytoalexin으로 알려진 capsidiol의 생합성을 촉매하는 5-epi-aristolochene hydroxylase는 cytochrome P450 (P450) 억제제인 ancymidol과 ketocornazol에 의해 그 활성이 특이적으로 억제되어, 이 효소가 P450계 효소임을 알 수 있었다. P450 효소가 공통으로 보유하는 염기서열을 지닌 primer를 이용하여 RT-PCR과 cDNA screening을 실시한 결과 고추배양세포에서 elicitor 처리에 의해 강하게 유도되는 cDNA (P450Hy01)를 cloning하였다. 배양세포에 cellulase, arachidonic acid, jasmonic acid, 자외선 등을 처리하여 capsidiol을 생합성하는 량과 P450Hy01 mRNA의 발현정도는 밀접한 유사성이 있었다. P450Hy01의 염기서열은 담배에서 밝혀진 5-epi-aristolochene-1,3-hydroxylase와 98%의 유사성이 있었으며, P450 효소가 공통으로 지니는 heme-binding domain인 FxxGxRxCxG를 보유하고 있었다 이러한 결과는 본 연구에서 cloning된 P450Hy01이 고추의 세포에서 capsidiol의 생합성을 촉매하는 5-epi-aristolochene hydroxylase 효소를 coding 하고 있음을 시사한다.
In order to measure the enzyme activity of 5-epi-aristolochene hydroxylase, one of cytochrome P450 (P450) enzymes in eicitor-treated pepper cell, we used in vivo assay method and demonstrated a dramatic suppression of the activity by P450-inhibitors, ancymidol and ketocornazole. Using RT-PCR method with degenerate primer of the well conserved domains found within most P450-enzymes, and using cDNA library screening method, one distinct cDNA, being designated P450Hy01, was successfully isolated from elicitor-treated pepper cells. P450Hy01 mRNA was all induced in elicitor-treated cells whereas never induced in control cells. Moreover, levels of P450Hy01 expression were highly correlated with the levels of extracellular capsidiol production by different elicitors in cell cultures. P450Hy01 transcript was also induced by several other elicitors such as, cellulase, arachidonic acid, jasmonic acid, yeast extract as well as UV stress. P450Hy01 sequence contained high probability amino acid matches to known Plant P450 genes and ORF with a conserved FxxGxRxCxG heme-binding domain. P450Hy01 cDNA showed 98% of homology in sequence of nucleotide as well as amino acid to 5-epi-aristolochene-1, 3-hydroxylase (5EAl, 3H) which has been isolated in tobacco cells, suggesting that P450Hy01 is prominent candidate gene for P450-enzyme encoding 5EAl, 3H in pepper cell.
