Two hundred thirteen cytochrome P450 (P450) genes were collected from bacteria and expressed based on an Escherichia coli expression system to test their hydroxylation ability to testosterone. Twenty-four P450s stereoselectively monohydroxylated testosterone at the 2alpha-, 2beta-, 6beta-, 7beta-, 11beta-, 12beta-, 15beta-, 16alpha-, and 17-positions (17-hydroxylation yields 17-ketoproduct). The hydroxylation site usage of the P450s is not the same as that of human P450s, while the 2alpha-, 2beta-, 6beta-, 11beta-, 15beta-, 16alpha-, and 17-hydroxylation are reactions common to both human and bacterial P450s. Most of the testosterone hydroxylation catalyzed by bacterial P450s is on the beta face.

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Background: (+)-Nootkatone (4) is a high added-value compound found in grapefruit juice. Allylic oxidation of the sesquiterpene (+)-valencene (1) provides an attractive route to this sought-after flavoring. So far, chemical methods to produce (+)-nootkatone (4) from (+)-valencene (1) involve unsafe toxic compounds, whereas several biotechnological approaches applied yield large amounts of undesirable byproducts. In the present work 125 cytochrome P450 enzymes from bacteria were tested for regioselective oxidation of (+)-valencene (1) at allylic C2-position to produce (+)-nootkatone (4) via cis-(2) or trans-nootkatol (3). The P450 activity was supported by the coexpression of putidaredoxin reductase (PdR) and putidaredoxin (Pdx) from Pseudomonas putida in Escherichia coli.

We are using directed evolution to extend the range of dioxygenase-catalyzed biotransformations to include substrates that are either poorly accepted or not accepted at all by the naturally occurring enzymes. Here we report on the oxidation of a heterocyclic substrate, 4-picoline, by toluene dioxygenase (TDO) and improvement of the enzyme's activity by laboratory evolution. The biotransformation of 4-picoline proceeds at only ϳ4.5% of the rate of the natural reaction on toluene. Random mutagenesis, saturation mutagenesis, and screening directly for product formation using a modified Gibbs assay generated mutant TDO 3-B38, in which the wild-type stop codon was replaced with a codon encoding threonine. Escherichia coli-expressed TDO 3-B38 exhibited 5.6 times higher activity toward 4-picoline and ϳ20% more activity towards toluene than wild-type TDO. The product of the biotransformation of 4-picoline is 3-hydroxy-4-picoline; no cis-diols of 4-picoline were observed.Dioxygenase enzymes involved in the catabolism of aromatic hydrocarbons by soil microorganisms nicely illustrate nature's ability to adapt to different carbon sources through evolution of the substrate specificity of the biodegradation enzymes (35). The biodegradation pathway often begins with the dioxygenasecatalyzed regio-and enantio-specific introduction of molecular oxygen into aromatic compounds to form the corresponding arene cis-diols, with consumption of NADH (13, 36) ( Fig. 1).It has been noted that the chiral products of the dioxygenase reaction can be converted in a variety of synthetic reactions to advanced intermediates for natural-product synthesis (8, 15). Toluene dioxygenase (TDO) from Pseudomonas putida readily dihydroxylates aromatic carbocycles with one or two small hydrophobic substituents (6, 33). Activity towards much larger, fused-ring substrates or substrates with polar or bulky substituents is considerably reduced or nonexistent (33).We are attempting to extend the utility of dioxygenase-catalyzed biotransformations by engineering the catalysts to accept a wider range of substrates, including small heterocyclic compounds and polar-substituted carbocyclic aromatics. N-Heterocyclic compounds are useful for the synthesis of biologically active compounds; recent reports describe the regioand/or stereo-controlled biooxidation of N-heterocycles (20,26). Bicyclic compounds such as quinolines and benzofurans are accepted by TDO, with oxygen insertion occurring primarily in the carbocylic rings (3-5).To date, reactions on single-ring heterocycles have not been reported. We have found that TDO catalyzes the oxygenation of 4-picoline (4-methylpyridine), although at a much slower rate than on its preferred substrate toluene.A strategy of DNA shuffling to create libraries of hybrid genes and screening has been used with some success to extend the substrate range of dioxygenases that degrade environmental pollutants such as polychlorinated biphenyls (7, 21). An alternative approach is to fine tune a single gene by accumulating beneficial mutat...

Kitasatospora setae NBRC 14216T (=KM-6054T) is known to produce setamycin (bafilomycin B1) possessing antitrichomonal activity. The genus Kitasatospora is morphologically similar to the genus Streptomyces, although they are distinguishable from each other on the basis of cell wall composition and the 16S rDNA sequence. We have determined the complete genome sequence of K. setae NBRC 14216T as the first Streptomycetaceae genome other than Streptomyces. The genome is a single linear chromosome of 8 783 278 bp with terminal inverted repeats of 127 148 bp, predicted to encode 7569 protein-coding genes, 9 rRNA operons, 1 tmRNA and 74 tRNA genes. Although these features resemble those of Streptomyces, genome-wide comparison of orthologous genes between K. setae and Streptomyces revealed smaller extent of synteny. Multilocus phylogenetic analysis based on amino acid sequences unequivocally placed K. setae outside the Streptomyces genus. Although many of the genes related to morphological differentiation identified in Streptomyces were highly conserved in K. setae, there were some differences such as the apparent absence of the AmfS (SapB) class of surfactant protein and differences in the copy number and variation of paralogous components involved in cell wall synthesis.

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Vitamin D 3 hydroxylase (Vdh) isolated from actinomycete Pseudonocardia autotrophica is a cytochrome P450 (CYP) responsible for the biocatalytic conversion of vitamin D 3 (VD 3 ) to 1␣,25-dihydroxyvitamin D 3 (1␣,25(OH) 2 VD 3 ) by P. autotrophica. Although its biological function is unclear, Vdh is capable of catalyzing the two-step hydroxylation of VD 3 , i.e. the conversion of VD 3 to 25-hydroxyvitamin D 3 (25(OH)VD 3 ) and then of 25(OH)VD 3 to 1␣,25(OH) 2 VD 3 , a hormonal form of VD 3 . Here we describe the crystal structures of wild-type Vdh (Vdh-WT) in the substrate-free form and of the highly active quadruple mutant (Vdh-K1) generated by directed evolution in the substrate-free, VD 3 -bound, and 25(OH)VD 3 -bound forms. Vdh-WT exhibits an open conformation with the distal heme pocket exposed to the solvent both in the presence and absence of a substrate, whereas Vdh-K1 exhibits a closed conformation in both the substrate-free and substrate-bound forms. The results suggest that the conformational equilibrium was largely shifted toward the closed conformation by four amino acid substitutions scattered throughout the molecule. The substratebound structure of Vdh-K1 accommodates both VD 3 and 25(OH)VD 3 but in an anti-parallel orientation. The occurrence of the two secosteroid binding modes accounts for the regioselective sequential VD 3 hydroxylation activities. Moreover, these structures determined before and after directed evolution, together with biochemical and spectroscopic data, provide insights into how directed evolution has worked for significant enhancement of both the VD 3 25-hydroxylase and 25(OH)VD 3 1␣-hydroxylase activities.3 is a B-ring opening secosteroid involved in a wide variety of biological functions in mammals (1). In humans, VD 3 is converted into its physiologically active form, 1␣,25-dihydroxyvitamin D 3 (1␣,25(OH) 2 VD 3 ), via hydroxylation reactions that are catalyzed by several cytochrome P450s (CYPs) (1, 2). The first hydroxylation is done at the C25 position of VD 3 by CYP27A1 (2, 3) and CYP2R1 (2, 4) in the liver to produce 25-hydroxyvitamin D 3 (25(OH)VD 3 ). The second proceeds at the C1␣ position of 25(OH)VD 3 by CYP27B1 in the kidney (5) (Fig. 1). The final product, 1␣,25(OH) 2 VD 3 , functions as a hormone with a critical role in maintaining calcium and phosphate homeostasis as well as in controlling the differentiation and proliferation of multiple cell types (1, 2, 6). Indeed, the many symptoms associated with VD 3 deficiency and the VD metabolic disorder, which include psoriasis, osteoporosis, rickets, and hypoparathyroidism, are treated using 1␣,25(OH) 2 VD 3 and its derivatives (1).Although the chemical synthesis of 1␣,25(OH) 2 VD 3 from cholesterol is an established method, it is inefficient, the maximum yield is no more than 1% (7). Alternatively, biocatalytic conversion by the actinomycete Pseudonocardia autotrophica is currently in practical use for the industrial production of 1␣,25(OH) 2 VD 3 (8, 9). We have recently cloned the gene encoding the VD 3 hydroxy...

Our biotransformation using Escherichia coli expressing a cytochrome P450 (CYP) belonging to the CYP153A family from Acinetobacter sp. OC4 produced a great amount of 1-octanol (2,250 mg per liter) from n-octane after 24 h of incubation. This level of production is equivalent to the maximum level previously achieved in biotransformation experiments of alkanes. In addition, the initial production rate of 1-octanol was maintained throughout the entire incubation period. These results indicate that we have achieved the functional and stable expression of a CYP in E. coli for the first time. Further, our biotransformation system showed alpha,omega-diterminal oxidation activity of n-alkanes, and a large amount of 1,8-octanediol (722 mg per liter) was produced from 1-octanol after 24 h of incubation. This is the first report on the bioproduction of alpha,omega-alkanediols from n-alkanes or 1-alkanols.