The human Short-chain Dehydrogenase Reductase (SDR) superfamily of oxoreductase enzymes facilitate a network of metabolic enzymes responsible for the regulation of key signalling molecules including fatty acids and cholesterol-derived steroids. Despite a few key family members with well characterised functions and causative relationships in human disease many family members remain poorly characterised. One such uncharacterised family member is 11βHSD1L and has been identified as a novel species-restricted SDR family member with a high level of protein sequence homology to 11βHSD1, an enzyme responsible for the bidirectional interconversion of the steroid hormones cortisol and cortisone. Only two papers have investigated this enzyme in any level of detail and these studies suggested that 11βHSD1L was strongly expressed in the brain. Detailed information on the enzymology of 11β-HSD1L is unavailable with preliminary assays suggesting novel bidirectional interconversion of cortisol and cortisone. We have further characterised the gene ontology and expression patterns of 11βHSD1L using various Bioinformatic tools, real-time and drop-digital qPCR and immunohistochemical analysis in the sheep, marmoset and macaque.
Conservation of two important enzyme catalytic domains was demonstrated through multiple sequence alignments and 3-dimensional homology modelling with significant levels of structural similarity between 11βHSD1L and 11βHSD1 including a highly conserved Rossmann fold pattern. Real-time qPCR analysis showed that HSD11B1L mRNA expression was highest in the ovary and pituitary in both adult and fetal sheep, with moderate to low expression levels observed in other major organs, including the intestinal tract. Finally, immunofluorescent techniques showed strong 11βHSD1L protein localisation to granulosa cells of the ovary, pituitary gonadotrophs, and in the gastrointestinal tract to the mucosa of both the small and large intestine. These results suggest that 11βHSD1L may play a role in reproductive steroid metabolism but further co-localisation data and substrate assays may suggest other metabolites as potential enzymatic targets.