Enhanced bioconversion of colchicine to regiospecific 3-demethylated colchicine (3-DMC) by whole cell immobilization of recombinant E. coli harboring P450 BM-3 gene

Oxidative biotransformation of stemofoline alkaloids

Biotransformations of stemofoline (1a), (2'S)-hydroxystemofoline (2a), (11Z)-1',2'-didehydrostemofoline (3a) and stemocurtisine (4) were studied through fermentation with Cunninghamella elegans TISTR 3370. Three new stemofoline derivatives; 6 R-hydroxystemofoline (1b), (2'S, 6 R)-dihydroxystemofoline (2b) and (11Z,6R)-1',2'-didehydro-6-hydroxystemofoline (3b), together with the known compound 1',2'-didehydrostemofoline-N-oxide (3c), were produced by C-hydroxylation and N-oxidation reactions. Stemocurtisine was not biotransformed under these conditions. The transformed product 1b was four times more potent (IC50 = 11.01 ± 1.49 µM) than its precursor 1a (IC50 = 45.1 ± 5.46 µM) as an inhibitor against acetylcholinesterase.

Regio- and enantioselective O-demethylation of tetrahydroprotoberberines by cytochrome P450 enzyme system from Streptomyces griseus ATCC 13273

Tetrahydroprotoberberines (THPBs), a class of naturally occurring isoquinoline alkaloids, contain substituent methoxyl or hydroxyl groups which play a significant role in the pharmacological properties of these molecules. In this study, we report a biocatalytic strategy for selective O-demethylation of THPBs. CYP105D1, a cytochrome P450 from Streptomyces griseus ATCC 13273, exhibited markedly regioselective demethylation of nonhydroxyl-THPBs and monohydroxyl-THPBs on the D-ring. A possible binding mode of THPBs with CYP105D1 was investigated by docking analysis, and the results revealed that the D-rings of THPBs were with the minimum distance to the heme iron. Tetrahydropalmatine was used as a model substrate and enantioselective demethylation was demonstrated. (S)-Tetrahydropalmatine was only demethylated at C-10, while (R)-tetrahydropalmatine was first demethylated at C-10 and then subsequently demethylated at C-9. The kcat/Km value for demethylation of (R)-tetrahydropalmatine by CYP105D1 was 3.7 times greater than that for demethylation of (S)-tetrahydropalmatine. Furthermore, selective demethylation of (S)-tetrahydropalmatine by the CYP105D1-based whole-cell system was demonstrated for the highly efficient production of (S)-corydalmine which has distinct pharmacological applications, such as providing relief from bone cancer pain and reducing morphine tolerance. Moreover, a homologous redox partner was identified to enhance the catalytic efficiency of the CYP105D1-based whole-cell system. This is the first enzymatic characterization of a cytochrome P450 that has regio- and enantioselective demethylation activity of THPBs for application purpose. The cytochrome P450 system could be a promising strategy for selective demethylation in the pharmaceutical industry.

Significantly enhanced substrate tolerance of Pseudomonas putida nitrilase via atmospheric and room temperature plasma and cell immobilization

The objective of the study was to enhance the substrate tolerance of Pseudomonas putida nitrilase via atmospheric and room temperature plasma (ARTP) and cell immobilization. The mutant library was constructed by ARTP and rapidly screened by an OPA-TCA microscale reaction. A mutant strain of mut-D3 was obtained and its optimum substrate concentration was improved to 150mM from 100mM. It could accumulate 189g/L nicotinic acid (NA) from 3-cyanopyridine (3-CP), which was increased by 42% compared with that of wild type (WT). Additionally, composite immobilization of mut-D3 was performed and SA-PVA immobilized cells could catalyze 250mM 3-CP each batch with finally accumulating 346g/L NA, while free cells accumulated 175g/L NA. These results indicated that the free or immobilized catalysts of mut-D3 could serve as a good choice for NA production. This is the first report on mutation breeding of nitrilase-producing microorganisms by ARTP.

Constrained azeotropic optimization of extraction system components for the safe and efficient recovery of a desired metabolite (e.g., 3-demethylated colchicine)

Constrained azeotropic optimization of extraction system components for the safe and efficient recovery of a desired metabolite (e.g., 3-DMC) using artificial learning and evolutionary optimization techniques.