Department of Biology, Indiana University-Purdue University Indianapolis, Indianapolis, IN 46202, USA.
Mol Plant. 2010 Jan;3(1):143-55. doi: 10.1093/mp/ssp091. Epub 2009 Nov 10.
The Arabidopsis FCLY gene encodes a specific farnesylcysteine (FC) lyase, which is responsible for the oxidative metabolism of FC to farnesal and cysteine. In addition, fcly mutants with quantitative decreases in FC lyase activity exhibit an enhanced response to ABA. However, the enzymological properties of the FCLY-encoded enzyme and its precise role in ABA signaling remain unclear. Here, we show that recombinant Arabidopsis FC lyase expressed in insect cells exhibits high selectivity for FC as a substrate and requires FAD and molecular oxygen for activity. Arabidopsis FC lyase is also shown to undergo post-translational N-glycosylation. FC, which is a competitive inhibitor of isoprenylcysteine methyltransferase (ICMT), accumulates in fcly mutants. Moreover, the enhanced response of fcly mutants to ABA is reversed by ICMT overexpression. These observations support the hypothesis that the ABA hypersensitive phenotype of fcly plants is the result of FC accumulation and inhibition of ICMT.
拟南芥 FCLY 基因编码一种特异的法呢基半胱氨酸（FC）裂解酶，该酶负责将 FC 氧化代谢为法呢醛和半胱氨酸。此外，FC 裂解酶活性定量降低的 fcly 突变体对 ABA 表现出增强的响应。然而，FCLY 编码的酶的酶学特性及其在 ABA 信号转导中的精确作用仍不清楚。在这里，我们表明在昆虫细胞中表达的重组拟南芥 FC 裂解酶对 FC 作为底物表现出高选择性，并需要 FAD 和分子氧才能发挥活性。还表明拟南芥 FC 裂解酶经历翻译后 N-糖基化。FC 是异戊烯基半胱氨酸甲基转移酶（ICMT）的竞争性抑制剂，在 fcly 突变体中积累。此外，FC 裂解酶活性增强的 fcly 突变体对 ABA 的响应通过 ICMT 过表达得到逆转。这些观察结果支持这样的假设，即 fcly 植物的 ABA 超敏表型是由于 FC 积累和 ICMT 抑制所致。
