Cysteine biosynthesis inLactobacillus casei: identification and characterization of a serine acetyltransferase

Abstract

In bacteria, cysteine can be synthesized from serine by two steps involving an L-serine O-acetyltransferase (SAT) and a cysteine synthase (CysK). While CysK is found in the publicly available annotated genome from Lactobacillus casei ATCC 334, a gene encoding SAT (cysE) is missing. In this study, we found that various strains of L. casei grew in a chemically defined medium containing sulfide as the sole sulfur source, indicating the presence of a serine O-acetyltransferase. The gene lying upstream of cysK is predicted to encode a homoserine trans-succinylase (metA). To study the function of this gene, it was cloned from L. casei FAM18110. The purified, recombinant protein did not acylate L-homoserine in vitro. Instead, it catalyzed the formation of O-acetyl serine from L-serine and acetyl-CoA. Furthermore, the plasmid expressing the L. casei gene complemented an Escherichia coli cysE mutant strain but not an E. coli metA mutant. This clearly demonstrated that the gene annotated as metA in fact encodes the SAT function and should be annotated as cysE.

Impacts of Desulfobacterales and Chromatiales on sulfate reduction in the subtropical mangrove ecosystem as revealed by SMDB analysis

“…L-cysteine production is the main pathway for microorganisms to absorb inorganic sulfur sources from their environment by converting sulfide into organic sulfur via assimilation. This finding was consistent with the abundance of adenylylsulfate kinase (cysC) and serine O-acetyltransferase (cysE) ( Supplementary Table S2), which are the key genes for cysteine synthesis (Bogicevic et al, 2016). In addition, Fe(III) is buried and acts as an oxidant for sulfide in deeper sediment layers where it partly binds the produced sulfide as iron sulfide (FeS) and pyrite (FeS2) (Canfield, 1989;Luther et al, 1986).…”

Lactobacillus acidophilus DDS-1 Modulates the Gut Microbiota and Improves Metabolic Profiles in Aging Mice

“…Cysteine and methionine are the only two sulfur-containing amino acids that integrate into proteins [ 55 ]. Accumulating evidence indicates that the intestinal metabolism of dietary sulfur-containing amino acids methionine and cysteine are nutritionally important for normal intestinal mucosal growth [ 56 ]. The cysteine and methionine metabolism pathway was upregulated in YP group, which could be associated with beneficial modulation of gut microbiota and basic metabolism of growth in youth [ 55 ].…”

Transcriptional Regulation of Cysteine and Methionine Metabolism in Lactobacillus paracasei FAM18149

“…Since the FAM18149 strain can grow in medium containing either sulfide, cysteine, or methionine as the sole sulfur source (Irmler et al, 2008 ; Bogicevic et al, 2016 ), the pathways for the conversion of cysteine to methionine and vice versa should be present. The FAM18149 genome was therefore searched for genes involved in the metabolism of these sulfur-containing amino acids.…”

“… c The gene name is designated as metA in L. paracasei ATCC 334. Since the gene in fact encodes a serine acetyltransferase (Bogicevic et al, 2016 ), the gene name cysE is used in this study. d The recombinant-produced protein also exhibited cystathionine gamma-synthase activity in vitro (Irmler et al, 2008 ).…”

“… c The gene name is designated as metA in L. paracasei ATCC 334. Since the gene in fact encodes a serine acetyltransferase (Bogicevic et al, 2016 ), the gene name cysE is used in this study. …”