Alternative Biotransformation of Retinal to Retinoic Acid or Retinol by an Aldehyde Dehydrogenase from Bacillus cereus

Abstract

A novel bacterial aldehyde dehydrogenase (ALDH) that converts retinal to retinoic acid was first identified inBacillus cereus. The amino acid sequence of ALDH fromB. cereus(BcALDH) was more closely related to mammalian ALDHs than to bacterial ALDHs. This enzyme converted not only small aldehydes to carboxylic acids but also the large aldehyde all-trans-retinal to all-trans-retinoic acid with NAD(P)+. We newly found thatBcALDH and human ALDH (ALDH1A1) could reduce all-trans-retinal to all-trans-retinol with NADPH. The catalytic residues inBcALDH were Glu266 and Cys300, and the cofactor-binding residues were Glu194 and Glu457. The E266A and C300A variants showed no oxidation activity. The E194S and E457V variants showed 15- and 7.5-fold higher catalytic efficiency (kcat/Km) for the reduction of all-trans-retinal than the wild-type enzyme, respectively. The wild-type, E194S variant, and E457V variant enzymes with NAD+converted 400 μM all-trans-retinal to 210 μM all-trans-retinoic acid at the same amount for 240 min, while with NADPH, they converted 400 μM all-trans-retinal to 20, 90, and 40 μM all-trans-retinol, respectively. These results indicate thatBcALDH and its variants are efficient biocatalysts not only in the conversion of retinal to retinoic acid but also in its conversion to retinol with a cofactor switch and that retinol production can be increased by the variant enzymes. Therefore,BcALDH is a novel bacterial enzyme for the alternative production of retinoic acid and retinol.IMPORTANCEAlthough mammalian ALDHs have catalyzed the conversion of retinal to retinoic acid with NAD(P)+as a cofactor, a bacterial ALDH involved in the conversion is first characterized. The biotransformation of all-trans-retinal to all-trans-retinoic acid byBcALDH and human ALDH was altered to the biotransformation to all-trans-retinol by a cofactor switch using NADPH. Moreover, the production of all-trans-retinal to all-trans-retinol was changed by mutations at positions 194 and 457 inBcALDH. The alternative biotransformation of retinoids was first performed in the present study. These results will contribute to the biotechnological production of retinoids, including retinoic acid and retinol.

Identification of a cyanobacterial aldehyde dehydrogenase that produces retinoic acid in vitro

“…This is consistent with the lack of function seen with the purified slr0091 [19]. The Bacillus cereus ALDH in our phylogenetic analysis shows a closer relationship with yeast ALDH and mammalian ALDH8 then it does with the cyanobacterial ALDH [25] Sequence alignment of cfALDH with the human ALDH1 indicates that the cyanobacterial protein contains the same GQCC motif as the human ALDH1 and ALDH2 proteins [24] ( Figure 1d, highlighted in red and Supplementary Figure 2). This motif is present in ALDH1/2 orthologues and these residues reside at the bottom of the substrate entry channel (SEC).…”

“…Sequences were chosen from [20] and [24], alongside the sequence of the previously studied Synechocystis sp. PCC 6803 ALDH (Slr0091) and ALDH from Bacillus subtilis which is the first bacterial aldehyde dehydrogenase to be identified that can convert retinal to retinoic acid [25]. Phylogenetic analysis indicated that the C. fritschii ALDH orthologue (henceforth cfALDH), which has 64% sequence identity with human ALDH1A1, groups with other previously identified cyanobacterial proteins (Figure 1b and Supplementary Figure 1).…”

“…Aldehyde dehydrogenase sequences were chosen from [20] and [24], along with the Bacillus subtillis ALDH from [25] and slr0091 from Synechocystis PCC 6803 [19]. Amino acid sequences were aligned using MUSCLE [37] in MEGA7 [38].…”

Alterations in Gut Vitamins and Amino Acids Metabolism are Associated with Symptoms and Neurodevelopment of Children with Autism Spectrum Disorders

“…ALDH1A family are key enzymes to oxidize retinal into RA, and XX Xu et al [22] found ASD patients with excessive UBE3A (an autism related gene and molecule) may have congenital errors of retinol metabolism, for excessive UBE3A can inhibit the activity of ALDH1A and compromised retinal oxidized to RA. Moreover, gut microbiota can take part in alternative biotransformation of retinal to retinol or RA [23].…”

“…Gut microbiota was an important role in the gut metabolism, for micro ora can produce vitamins and participant in the metabolic of numerous substances [49] [23]. Inadequate intake from food could also partly explain the decreased of multiple vitamins and amino acids.…”