Tschantz W R, Digits J A, Pyun H J, Coates R M, Casey P J
Departments of Pharmacology and Cancer Biology and Biochemistry, Duke University Medical Center, Durham, North Carolina 27710, USA.
J Biol Chem. 2001 Jan 26;276(4):2321-4. doi: 10.1074/jbc.C000616200. Epub 2000 Nov 14.
Prenylated proteins contain either a 15-carbon farnesyl or a 20-carbon geranylgeranyl isoprenoid covalently attached via a thioether bond to a cysteine residue at or near their C terminus. As prenylated proteins comprise up to 2% of the total protein in eukaryotic cells, and the thioether bond is a stable modification, their degradation raises a metabolic challenge to cells. A lysosomal enzyme termed prenylcysteine lyase has been identified that cleaves prenylcysteines to cysteine and an unidentified isoprenoid product. Here we show that the isoprenoid product of prenylcysteine lyase is the C-1 aldehyde of the isoprenoid moiety (farnesal in the case of C-15). The enzyme requires molecular oxygen as a cosubstrate and utilizes a noncovalently bound flavin cofactor in an NAD(P)H-independent manner. Additionally, a stoichiometric amount of hydrogen peroxide is produced during the reaction. These surprising findings indicate that prenylcysteine lyase utilizes a novel oxidative mechanism to cleave thioether bonds and provide insight into the unique role this enzyme plays in the cellular metabolism of prenylcysteines.
异戊二烯化蛋白含有一个15碳的法尼基或一个20碳的香叶基香叶基类异戊二烯，它们通过硫醚键与位于其C末端或附近的半胱氨酸残基共价连接。由于异戊二烯化蛋白占真核细胞总蛋白的比例高达2%，且硫醚键是一种稳定的修饰，它们的降解给细胞带来了代谢挑战。一种名为异戊二烯半胱氨酸裂解酶的溶酶体酶已被鉴定出来，它能将异戊二烯半胱氨酸裂解为半胱氨酸和一种未知的类异戊二烯产物。在这里，我们表明异戊二烯半胱氨酸裂解酶的类异戊二烯产物是类异戊二烯部分的C-1醛（对于C-15来说是法呢醛）。该酶需要分子氧作为共底物，并以不依赖NAD(P)H的方式利用非共价结合的黄素辅因子。此外，反应过程中会产生化学计量的过氧化氢。这些惊人的发现表明，异戊二烯半胱氨酸裂解酶利用一种新的氧化机制来裂解硫醚键，并为该酶在异戊二烯半胱氨酸细胞代谢中所起的独特作用提供了见解。
