Piotrowski Markus
Department of Plant Physiology, Ruhr-Universität Bochum, Universitätsstrasse 150, 44801 Bochum, Germany.
Phytochemistry. 2008 Nov;69(15):2655-67. doi: 10.1016/j.phytochem.2008.08.020. Epub 2008 Oct 6.
The potential of plant nitrilases to convert indole-3-acetonitrile into the plant growth hormone indole-3-acetic acid has earned them the interim title of "key enzyme in auxin biosynthesis". Although not widely recognized, this view has changed considerably in the last few years. Recent work on plant nitrilases has shown them to be involved in the process of cyanide detoxification, in the catabolism of cyanogenic glycosides and presumably in the catabolism of glucosinolates. All plants possess at least one nitrilase that is homologous to the nitrilase 4 isoform of Arabidopsis thaliana. The general function of these nitrilases lies in the process of cyanide detoxification, in which they convert the intermediate detoxification product beta-cyanoalanine into asparagine, aspartic acid and ammonia. Cyanide is a metabolic by-product in biosynthesis of the plant hormone ethylene, but it may also be released from cyanogenic glycosides, which are present in a large number of plants. In Sorghum bicolor, an additional nitrilase isoform has been identified, which can directly use a catabolic intermediate of the cyanogenic glycoside dhurrin, thus enabling the plant to metabolize its cyanogenic glycoside without releasing cyanide. In the Brassicaceae, a family of nitrilases has evolved, the members of which are able to hydrolyze catabolic products of glucosinolates, the predominant secondary metabolites of these plants. Thus, the general theme of nitrilase function in plants is detoxification and nitrogen recycling, since the valuable nitrogen of the nitrile group is recovered in the useful metabolites asparagine or ammonia. Taken together, a picture emerges in which plant nitrilases have versatile functions in plant metabolism, whereas their importance for auxin biosynthesis seems to be minor.
植物腈水解酶将吲哚 - 3 - 乙腈转化为植物生长激素吲哚 - 3 - 乙酸的潜力，为它们赢得了“生长素生物合成中的关键酶”这一临时称号。尽管这一观点尚未得到广泛认可，但在过去几年中已发生了很大变化。最近关于植物腈水解酶的研究表明，它们参与氰化物解毒过程、生氰糖苷的分解代谢，并且可能还参与硫代葡萄糖苷的分解代谢。所有植物都至少拥有一种与拟南芥腈水解酶4亚型同源的腈水解酶。这些腈水解酶的一般功能在于氰化物解毒过程，在此过程中它们将中间解毒产物β - 氰基丙氨酸转化为天冬酰胺、天冬氨酸和氨。氰化物是植物激素乙烯生物合成中的一种代谢副产物，但它也可能从大量植物中存在的生氰糖苷中释放出来。在双色高粱中，已鉴定出一种额外的腈水解酶亚型，它可以直接利用生氰糖苷百脉根苷的分解代谢中间体，从而使植物能够在不释放氰化物的情况下代谢其生氰糖苷。在十字花科植物中，已经进化出了一族腈水解酶，其成员能够水解硫代葡萄糖苷的分解代谢产物，而硫代葡萄糖苷是这些植物中主要的次生代谢产物。因此，植物中腈水解酶功能的总体主题是解毒和氮循环，因为腈基团中有价值的氮在有用的代谢产物天冬酰胺或氨中得以回收。综上所述，一幅图景浮现出来：植物腈水解酶在植物代谢中具有多种功能，而它们对生长素生物合成的重要性似乎较小。
