No abstract

A recombinant protein expression system working at low temperatures is expected to be useful for the production of thermolabile proteins. We constructed a low-temperature expression system using an Antarctic cold-adapted bacterium, Shewanella sp. strain Ac10, as the host. We evaluated the promoters for proteins abundantly produced at 4°C in this bacterium to express foreign proteins. We used 27 promoters and a broad-host-range vector, pJRD215, to produce ␤-lactamase in Shewanella sp. strain Ac10. The maximum yield was obtained when the promoter for putative alkyl hydroperoxide reductase (AhpC) was used and the recombinant cells were grown to late stationary phase. The yield was 91 mg/liter of culture at 4°C and 139 mg/liter of culture at 18°C. We used this system to produce putative peptidases, PepF, LAP, and PepQ, and a putative glucosidase, BglA, from a psychrophilic bacterium, Desulfotalea psychrophila DSM12343. We obtained 48, 7.1, 28, and 5.4 mg/liter of culture of these proteins, respectively, in a soluble fraction. The amounts of PepF and PepQ produced by this system were greater than those produced by the Escherichia coli T7 promoter system.

Hydroxypipecolic acids are bioactive compounds widely distributed in nature and are valuable building blocks for the organic synthesis of pharmaceuticals. We have found a novel hydroxylating enzyme with activity toward L-pipecolic acid (L-Pip) in a filamentous fungus, Fusarium oxysporum c8D. The enzyme L-Pip trans-4-hydroxylase (Pip4H) of F. oxysporum (FoPip4H) belongs to the Fe(II)/␣-ketoglutarate-dependent dioxygenase superfamily, catalyzes the regio-and stereoselective hydroxylation of L-Pip, and produces optically pure trans-4-hydroxy-L-pipecolic acid (trans-4-L-HyPip). Amino acid sequence analysis revealed several fungal enzymes homologous with FoPip4H, and five of these also had L-Pip trans-4-hydroxylation activity. In particular, the homologous Pip4H enzyme derived from Aspergillus nidulans FGSC A4 (AnPip4H) had a broader substrate specificity spectrum than other homologues and reacted with the L and D forms of various cyclic and aliphatic amino acids. Using FoPip4H as a biocatalyst, a system for the preparative-scale production of chiral trans-4-L-HyPip was successfully developed. Thus, we report a fungal family of L-Pip hydroxylases and the enzymatic preparation of trans-4-L-HyPip, a bioactive compound and a constituent of secondary metabolites with useful physiological activities.H ydroxypipecolic acids (HyPips) are naturally occurring sixmembered heterocyclic hydroxy amino acids that are widely distributed in nature. For instance, 4-hydroxy-, 5-hydroxy-, and 4,5-dihydroxypipecolic acids have been found in various members of the plant family (1-4). Likewise, 5-hydroxypipecolic acid was found to be present in mammalian brain and blood (5). HyPips are also components of some peptide antibiotics, terpenoids, and alkaloids, for example, Thus, the enzymatic hydroxylation of L-Pip was achieved as a side reaction of L-proline hydroxylase. To date, specific L-Piphydroxylating enzymes have not been reported, despite the fact that HyPips are important metabolites found in plants and mammals. In the present study, we identified and characterized L-Pip hydroxylases broadly conserved in some filamentous fungi. We found that the newly discovered L-Pip hydroxylases were particularly suitable biocatalysts for the asymmetric hydroxylation of cyclic amino acids, such as pipecolic acids and prolines. Moreover, the widespread distribution of genes encoding L-Pip hydroxylases indicates some important physiological roles of fungal secondary metabolites related to trans-4-L-HyPip. MATERIALS AND METHODSStrains and culture. Microorganisms isolated from soil and plant samples were cultured in GP medium comprised of 0.15% (wt/vol) KH 2 PO 4 , 0.05% (wt/vol) K 2 HPO 4 , 0.1% (wt/vol) NH 4 Cl, 0.03% (wt/vol) MgSO 4 ·7H 2 O, 0.01% (wt/vol) yeast extract, 0.025% (wt/vol) glucose, and 0.1% (wt/vol) L-Pip (pH 7.0) and grown at 28°C with shaking. Escherichia coli JM109 and Rosetta2(DE3) (Novagen, WI, USA) were used as host strains for the overexpression of the recombinant enzymes and cultured at 28°C in LB medium, comprised of 1% (wt/v...