Sulfite oxidation in Sinorhizobium meliloti
Jeremy J Wilson1, Ulrike Kappler
1Centre for Metals in Biology, School of Chemistry and Molecular Biosciences, The University of Queensland, St. Lucia, Qld 4072, Australia.
Biochimica Et Biophysica Acta
|July 28, 2009
Summary
Sulfite-oxidizing enzymes (SOEs) are vital for sulfur metabolism in bacteria. This study identifies SorT as the primary SOE in Sinorhizobium meliloti, revealing its unique characteristics and operon structure.
Area of Science:
- Microbiology
- Biochemistry
- Enzymology
Background:
- Sulfite-oxidizing enzymes (SOEs) are critical for sulfur compound metabolism in bacteria.
- Limited knowledge exists regarding the diversity and metabolic functions of SOEs.
- Sinorhizobium meliloti possesses four candidate SOE genes from three distinct types.
Purpose of the Study:
- To investigate the role of SOEs in Sinorhizobium meliloti.
- To explore the potential link between SOEs and taurine metabolism.
- To characterize the identified SOE and its associated electron acceptors.
Main Methods:
- Enzyme activity assays under various growth conditions.
- Protein purification and characterization of the key SOE.
- Kinetic analysis (kcat, KM) and pH-dependent studies.
- Phylogenetic analysis of related enzymes.
Main Results:
- Growth on taurine and thiosulfate induced high SOE activity, though thiosulfate is not metabolized.
- A single group 2 SOE, SorT (SMc04049), was identified as responsible for the observed activity.
- SorT is a novel, heme-free periplasmic homodimer with high affinity for sulfite and ferricyanide.
- SorT's sulfite affinity is pH-invariant, unlike other characterized SOEs.
- SorT is part of an operon including genes for a cytochrome c and azurin, potential electron acceptors.
- No phylogenetic link was found between SorT-related SOEs and taurine degradation enzymes.
Conclusions:
- SorT is the primary sulfite-oxidizing enzyme in S. meliloti, exhibiting unique biochemical properties.
- The SorT enzyme and its associated electron transport chain components (cytochrome c, azurin) are likely involved in sulfur compound oxidation.
- Despite induction by taurine, SorT does not appear to be directly involved in taurine degradation in S. meliloti.
More Related Videos
12:08Monitoring the Reductive and Oxidative Half-Reactions of a Flavin-Dependent Monooxygenase using Stopped-Flow Spectrophotometry
Published on: March 18, 2012
08:31Anaerobic Protein Purification and Kinetic Analysis via Oxygen Electrode for Studying DesB Dioxygenase Activity and Inhibition
Published on: October 3, 2018
Related Concept Videos
01:20Sulfur Assimilation
Sulfur is an essential element in biological systems, contributing to synthesizing key biomolecules, including amino acids such as cysteine and methionine, and cofactors such as coenzyme A and biotin. Microorganisms primarily assimilate sulfur as sulfate (SO₄²⁻) from the environment, which must undergo a series of biochemical transformations before it can be incorporated into cellular components. As sulfate is highly oxidized, it must undergo assimilatory sulfate reduction to become...
01:29Microbes and the Sulfur Cycle
Sulfur is a vital element in Earth's biogeochemical systems. It transitions through various inorganic states, including sulfate (SO₄²⁻), elemental sulfur (S⁰), and sulfide (S²⁻). Abiotic and biological mechanisms across oxic and anoxic environments intricately mediate these transformations. Sulfate, the most oxidized form of sulfur, is predominantly stored in rocks, marine sediments, and oceanic waters, acting as a long-term reservoir in the global sulfur cycle.In oxic environments,...
01:46The Calvin Benson Cycle
Ribulose 1,5- bisphosphate carboxylase/oxygenase (RuBisCo) is a critical enzyme that catalyzes carbon dioxide assimilation during photosynthesis. However, it is an inefficient enzyme, having an extremely slow catalytic rate. A typical enzyme can process about a thousand molecules per second; however, RuBisCo fixes only around three-carbon dioxides per second. Photosynthetic cells compensate for this slow rate by synthesizing very high amounts of RuBisCo, making it the most abundant single...
01:22Electrophilic Aromatic Substitution: Sulfonation of Benzene
Sulfonation of benzene is a reaction wherein benzene is treated with fuming sulfuric acid at room temperature to produce benzenesulfonic acid. Fuming sulfuric acid is a mixture of sulfur trioxide and concentrated sulfuric acid.
01:30Anoxygenic Photosynthesis
Anoxygenic photosynthesis is a phototrophic process that captures light energy to drive carbon fixation without producing molecular oxygen. Unlike oxygenic photosynthesis, which utilizes water as an electron donor and releases oxygen, anoxygenic phototrophs use alternative electron donors such as hydrogen sulfide (H₂S), elemental sulfur (S⁰), or thiosulfate (S₂O₃²⁻). This process is carried out by diverse groups of bacteria, including purple bacteria, green sulfur bacteria, heliobacteria, and...
02:26Preparation and Reactions of Sulfides
Sulfides are the sulfur analog of ethers, just as thiols are the sulfur analog of alcohol. Like ethers, sulfides also consist of two hydrocarbon groups bonded to the central sulfur atom. Depending upon the type of groups present, sulfides can be symmetrical or asymmetrical. Symmetrical sulfides can be prepared via an SN2 reaction between 2 equivalents of an alkyl halide and one equivalent of sodium sulfide.