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We have cloned, sequenced, and expressed the gene for a unique ATP-and NADPH-dependent carboxylic acid reductase (CAR) from a Nocardia species that reduces carboxylic acids to their corresponding aldehydes. Recombinant CAR containing an N-terminal histidine affinity tag had K m values for benzoate, ATP, and NADPH that were similar to those for natural CAR, and recombinant CAR reduced benzoic, vanillic, and ferulic acids to their corresponding aldehydes. car is the first example of a new gene family encoding oxidoreductases with remote acyl adenylation and reductase sites.Aromatic, aliphatic, and alicyclic aldehydes and alcohols are useful intermediates in the chemical, pharmaceutical, and food industries. Chemical methods for carboxylic acid reductions are limited, and they usually require prior derivatization and product deblocking with reactants containing competing functional groups. Biocatalytic reductions of carboxylic acids are attractive because the substrates are water soluble, blocking chemistry is not necessary, reductions are enantiospecific, and the scope of the reaction is very broad (24, 32).Although microbial reductions of carboxylic acids, usually producing the acids' corresponding aldehydes or alcohols, have been observed with whole-cell reactions of bacteria and fungi (3,4,6,8,20,22,24,25,30,(36)(37)(38)40), enzymatic reductions of carboxylic acids are relatively new and unexploited biocatalytic reactions of great potential value in organic synthesis (12).Aldehyde oxidoreductases, also known as carboxylic acid reductases (CAR), require ATP, Mg 2ϩ , and NADPH as cofactors (16,17,18,21,24). The reduction is a stepwise process involving initial binding of both ATP and the carboxylic acid to the enzyme in order to form mixed 5Ј-adenylic acid-carbonyl anhydride intermediates (9,15,25,27,39) that are subsequently reduced by hydride delivery from NADPH to form aldehyde products (16,25) (Fig. 1). Aromatic CARs have been purified to homogeneity only from Neurospora (17) and Nocardia (21, 24) species. Although N-terminal and internal amino acid sequences were reported for our Nocardia enzyme (24), sequences have never been determined for any gene coding for CARs. CAR from Nocardia sp. strain NRRL 5646 has an extremely wide substrate range, and it enantiospecifically reduces carboxylic acids (8,24,32). We report here the cloning and expression of the first CAR gene, car, and the use of cloned enzyme in vitro and in vivo to reduce carboxylic acid substrates.Strains, plasmids, media, and growth. Bacteria and plasmids used in this study are listed in Table 1. Nocardia sp. strain NRRL 5646 (14) was grown at 30°C in Luria-Bertani (LB) medium containing 0.05% Tween 80 (vol/vol [liquid medium only]). With Escherichia coli as the recombinant host for pHAT-based vectors, cells were grown at 37°C on solid or in liquid LB medium. Ampicillin (100 g/ml) was incorporated into LB medium to select for recombinants, and isopropyl-␤-D-thiogalactopyranoside (IPTG) (1 mM) and/or 5-bromo-4-chloro-3-indolyl-␤-D-galactopyranosi...

The microbiome can be defined as the community of microorganisms that live in a particular environment. Metagenomics is the practice of sequencing DNA from the genomes of all organisms present in a particular sample, and has become a common method for the study of microbiome population structure and function. Increasingly, researchers are finding novel genes encoded within metagenomes, many of which may be of interest to the biotechnology and pharmaceutical industries. However, such “bioprospecting” requires a suite of sophisticated bioinformatics tools to make sense of the data. This review summarizes the most commonly used bioinformatics tools for the assembly and annotation of metagenomic sequence data with the aim of discovering novel genes.

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