Sulfoacetate Is Degraded via a Novel Pathway Involving Sulfoacetyl-CoA and Sulfoacetaldehyde in Cupriavidus necator H16

Abstract

Bacterial degradation of sulfoacetate, a widespread natural product, proceeds via sulfoacetaldehyde and requires a considerable initial energy input. Whereas the fate of sulfoacetaldehyde in Cupriavidus necator (Ralstonia eutropha) H16 is known, the pathway from sulfoacetate to sulfoacetaldehyde is not. The genome sequence of the organism enabled us to hypothesize that the inducible pathway, which initiates sau (sulfoacetate utilization), involved a four-gene cluster (sauRSTU; H16_A2746 to H16_A2749). The sauR gene, divergently orientated to the other three genes, probably encodes the transcriptional regulator of the presumed sauSTU operon, which is subject to inducible transcription. SauU was tentatively identified as a transporter of the major facilitator superfamily, and SauT was deduced to be a sulfoacetate-CoA ligase. SauT was a labile protein, but it could be separated and shown to generate AMP and an unknown, labile CoA-derivative from sulfoacetate, CoA, and ATP. This unknown compound, analyzed by MALDI-TOF-MS, had a relative molecular mass of 889.7, which identified it as protonated sulfoacetyl-CoA (calculated 889.6). SauS was deduced to be sulfoacetaldehyde dehydrogenase (acylating). The enzyme was purified 175-fold to homogeneity and characterized. Peptide mass fingerprinting confirmed the sauS locus (H16_A2747). SauS converted sulfoacetyl-CoA and NADPH to sulfoacetaldehyde, CoA, and NADP ؉ , thus confirming the hypothesis.

Characterization of Carboxylic Acid Reductases for Biocatalytic Synthesis of Industrial Chemicals

“…Chemical reduction of a carboxylate to an aldehyde group is an energetically demanding reaction that is also hard to control because of the low energy barrier for the further reduction of the aldehyde product into an alcohol. Three biological routes are currently known to accomplish this challenging transformation: 1) single‐enzyme‐catalyzed direct reduction, 2) a two‐enzyme cascade through a coenzyme A thioester intermediate, and 3) a two‐enzyme cascade through a phosphoester intermediate . Single‐enzyme‐catalyzed reactions present a simpler and more practical option than the two‐enzyme systems, even though two‐enzyme cascades (route 2) have been well explored in microbial production of energy and industrial molecules such as n ‐butanol and butane‐1,4‐diol .…”

A genome-wide approach for identification and characterisation of metabolite-inducible systems

“…With exception of the acetoin-and 3-HP-inducible systems 25,47 , we identify and characterise 14 systems from C. necator. Two previously proposed regulators 48,49 , responding to tartrate and sulfonatoacetate, were experimentally validated to be involved in transcription activation of their corresponding metabolic genes in this study. Furthermore, here, we report inducible systems (OapR/P H16_RS01330 and PhgR/P H16_RS05530 ) responding to βalanine and phenylglyoxylate.…”

Paracoccus denitrificans PD1222 Utilizes Hypotaurine via Transamination Followed by Spontaneous Desulfination To Yield Acetaldehyde and, Finally, Acetate for Growth

“…The genome of P. denitrificans PD1222 (two chromosomes) harbors three candidate gene clusters for organosulfonate degradation (Table 1), first the taurine operon (transport, TauXY, Xsc, Pta, and sulfite export) (chromosome 1) and then a gene cluster each for isethionate (chromosome 2) and sulfoacetate (chromosome 1) degradation, based on our previous work with orthologous gene clusters (9,60,61). The three desulfonation pathways would converge at the level of sulfoacetaldehyde, but each of these clusters (presumed operons) contains its own set of Xsc and Pta genes (Table 1), which share up to 99% sequence identity.…”