Identification and characterization of 3-ketosphinganine reductase activity encoded at the BT_0972 locus in Bacteroides thetaiotaomicron

Lipidomic analysis reveals differences inBacteroidesspecies driven largely by plasmalogens, glycerophosphoinositols and certain sphingolipids

“…In this study, SP were found to represent between 19% (B. ovatus ) and 29% ( B. vulgatus ) of the total lipids detected (Figure 2A). The SP biosynthetic pathway in Bacteroides has been recently described and dihydroCer has been identified as a key intermediate (Stankeviciute et al ., 2022; Lee et al ., 2022). In our study dihydroCer was shown to account for approx.…”

“…These intermediates may be generated by the reduction of keto-sph by a keto-reductase and/or the hydrolysis of dihydroCer by ceramidases (Figure 3A & C). Recent studies have suggested that there may be multiple pathways for SP biosynthesis in Bacteroides and the varying levels of intermediates detected across the 4 species examined in this study does support this observation (Stankeviciute et al ., 2022; Lee et al ., 2022).…”

“…The biosynthesis of bacterial SP is initiated by serine palmitoyltransferase (SPT) which catalyses a reaction between a fatty acyl-CoA and serine, or alternatively alanine, to form keto-sph, or deoxy-keto-sph, respectively. The pathway to dihydroCer synthesis may proceed via that observed in eukaryotes i.e., via keto reductase activity (Lee et al ., 2022) to form sph or alternatively bacterial Cer synthase (CerS) directly adds an acyl chain to 3-keto-sph producing an oxidised dihydroCer intermediate (ox-dihydroCer) which is then reduced to dihydroCer by bacterial Cer reductase (CerR) (Stankeviciute et al, 2021). DihydroCer represents the central hub of SP metabolism and undergoes modification with different head groups to produce the uniquely bacterial SP, Cer PE, Cer PI and α-GalCer (Brown et al ., 2019; Wieland Brown et al ., 2013).…”

“…This highlights potentially important species-specific differences in enzyme kinetics and flux through the SP biosynthetic pathway. The presence of sph and deoxy-sph in B. thetaiotaomicron and B. ovatus may be indicative of increased keto-reductase activity (Lee et al ., 2022) and/or a slower rate of conversion to dihydroCer in these Bacteroides species. It may also be interpreted to indicate the presence of a ceramidase, absent in B. fragilis and B. vulgatus , that hydrolyses dihydroCer to sph (Stankevicute et al ., 2021).…”

Biochemical characterization of the first step in sulfonolipid biosynthesis in Alistipes finegoldii

“…Lee et al. ( 32 ) identified an enzyme (BT_0972) with 3-ketosphinganine reductase activity from a biochemical screen, and the amino acid sequence contains conserved features of NAD(P)H-dependent short-chain dehydrogenases/reductases. Additional experiments are needed to validate the sequence of reactions in bacterial sphingolipid synthesis; however, regardless of the sequence of steps, the consensus view is that the first step in sulfonolipid synthesis is catalyzed by an Spt-like condensation enzyme that remains to be biochemically or structurally characterized ( 29 , 30 , 31 ) ( Fig.…”