Identification of the diterpene cyclase and elucidation of early steps in the pseudopterosin biosynthetic pathway.

摘要

The pseudopterosins and seco-pseudopterosins are diterpene glycosides isolated from the marine soft coral, Pseudopterogorgia elisabethae . These compounds exhibit anti-inflammatory and analgesic activity greater than the industry standard, indomethacin. The overall goal of this research was to complete biosynthetic studies and enzymology related to the development of a biotechnological production method of the pseudopterosins and seco-pseudopterosins. We aimed to examine early steps in the biosynthetic pathway in order to gain detailed knowledge of the biosynthesis and enzymology of the system. Prior to examination of the biosynthetic pathway leading to the pseudopterosins, we developed both in vivo and in vitro systems to test putative precursors and demonstrated that pseudopterosin A is a precursor to pseudopterosins B–D.; We also identified and confirmed the intermediacy of the pseudopterosin diterpene cyclase product using a radioactivity-guided isolation. The bicyclic structure of the diterpene cyclase product suggests that the pseudopterosins and seco-pseudopterosins are derived from this common bicyclic intermediate. The isolation of the pseudopterosin diterpene cyclase product provided us with an assay for the purification of the enzyme involved in its production. We identified the diterpene cyclase in aqueous extracts of P. elisabethae and plan to utilize the amino acid sequence for identification of the gene. This represents the first isolation of a biosynthetic enzyme from a marine coral. Moreover, various characterization studies indicated that the enzyme displays certain similar characteristics to other terpenoid cyclases isolated from terrestrial sources.; In previous investigations, P. elisabethae was found only in the Bahamian and West Indian region, but we discovered P. elisabethae in the Florida Keys. Furthermore, due to the distinctive chemistry in the Florida Keys P. elisabethae, plausible early biosynthetic intermediates were isolated that are not present in the Bahamian population. We evaluated these compounds as intermediates in the biosynthesis of the pseudopterosins. The data obtained further supports the assumption of a common biosynthetic origin of the pseudopterosins and seco-pseudopterosins.