Analysis of the cryptophycin P450 epoxidase reveals substrate tolerance and cooperativity.

ABSTRACT: Cryptophycins are potent anticancer agents isolated from Nostoc sp. ATCC 53789 and Nostoc sp. GSV 224. The most potent natural cryptophycin analogues retain a beta-epoxide at the C2'-C3' position of the molecule. A P450 epoxidase encoded by c rpE recently identified from the cryptophycin gene cluster was shown to install this key functional group into cryptophycin-4 (Cr-4) to produce cryptophycin-2 (Cr-2) in a regio- and stereospecific manner. Here we report a detailed characterization of the CrpE epoxidase using an engineered maltose binding protein (MBP)-CrpE fusion. The substrate tolerance of the CrpE polypeptide was investigated with a series of structurally related cryptophycin analogues generated by chemoenzymatic synthesis. The enzyme specifically installed a beta-epoxide between C2' and C3' of cyclic cryptophycin analogues. The kcat/Km values of the enzyme were determined to provide further insights into the P450 epoxidase catalytic efficiency affected by substrate structural variation. Finally, binding analysis revealed cooperativity of MBP-CrpE toward natural and unnatural desepoxy cryptophycin substrates.

SUBMITTER: Ding Y 

PROVIDER: S-EPMC2697446 | biostudies-literature | 2008 Apr

REPOSITORIES: biostudies-literature