Phenylacetaldehyde reductase

Many aldehyde reductases transform both aldehydes and ketones. For example, phenylacetaldehyde reductase (PAR) from a styrene-assimilating Corynebacterium strain, ST-10, reduces hexyl aldehyde and phenylacetaldehyde [22aj. Other aldehyde reductases such as one from Sporobolomyces salmonicolor also reduce aldehydes as well as ketones [22b]. 

Figure 8.35 Reduction of ketones with phenylacetaldehyde reductase from Corynebacterium strain ST-10 [26].

The phenylacetaldehyde reductase involved in the degradation of styrene is also able to accept long-chain aliphatic aldehydes and ketones, and halogenated acetophenones (Itoh et al. 1997). 

Itoh N, R Morihama, J Wang, K Okada, N Mizngnchi (1997) Pnrification and characterization of phenylacetaldehyde reductase from a styrene-assimilating Corynebacterium strain, ST-10. Appl Environ Microbiol 63 3783-3788. 

Table 15-18. Examples of substrates of phenylacetaldehyde reductase from Corynebacterium strain, ST-10138.

Itoh, N., Mizuguchi, N., and Mabuchi, M. (1999) Production of chiral alcohols by enantioselective reduction with NADH-dependent phenylacetaldehyde reductase from Corynehacterium strain, ST-10, y. Mol Catcd., B Enzym., 6, 41-50. 

Dairi, T, and Itoh, N. (1999) Cloning, sequence analysis, and expression in Escherichia coli of the gene encoding phenylacetaldehyde reductase from styrene-assimilating Corynehacterium sp. strain ST-10. Appl. Microbiol Biotechnol,... 

Itoh, N., Matsuda, M., Mabuchi., M., Dairi, T., and Wang, J.-C. (2002) Chiral alcohol production by NADH-dependent phenylacetaldehyde reductase coupled with in situ regeneration of NADH. Eur. J. Biochem., 269,2394-2402. 

Makino, Y, Inoue, K., Dairi, T., and Itoh, N. (2005) Engineering of phenylacetaldehyde reductase for efficient substrate conversion in concentrated 2-propanol. Appl. Environ. Microbiol, 71, 4713 720. 

Mutated Rhodococcus phenylacetaldehyde reductase (PAR) or Leifsonia alcohol dehydrogenase (LSADH) were applied to water-soluble ketone substrates. For example, 4-hydroxy-2-butanone was reduced to (S)/(R)-l,3-butanediol, with a high yield and stereoselectivity. Intact E coli cells overexpressing mutated PAR (Sar268) or LSADH were directly immobilized with polyethyleneimine or 1,6-hexanediamine and glutaraldehyde and evaluated in a batch reactor. This system produced (S)-l,3-butanediol (87% ee) with a space-time yield (STY) of 12.5 mg/h/mL catalyst or (R)-l,3-butanediol (99% ee.) with an STY of 60.3 mg/h/mL catalyst. The immobilized cells in a packed bed reactor continuously produced (R)-l,3-butanediol with a yield of 99% (about 49.5 g/L) from 5% (w/v) 4-hydroxy-2-butanoate over 500 h. The concentration of PEI used for immobilization influenced the operational stability of immobilized cells, and the cells treated with 3% PEI showed better stability than those treated with lower PEI concentrations The immobilized E. coli biocatalyst could be used more than 30 times (for about 500 h) with no decrease in conversion [54]. 

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