Sulfate-reducing pathway in Escherichia coli involving bound intermediates

Area of Science:

• Microbiology
• Biochemistry

Background:

• Sulfate reduction is crucial for microbial metabolism.
• Previous studies suggested free sulfite and sulfide pathways in Escherichia coli.
• A bound intermediate pathway was known in Chlorella.

Purpose of the Study:

• To investigate the sulfate reduction pathway in Escherichia coli.
• To identify enzymes and intermediates involved in bound sulfate reduction.
• To compare the E. coli pathway with that of Chlorella.

Main Methods:

• Enzyme assays using E. coli extracts.
• Characterization of sulfotransferase activity.
• Analysis of thioredoxin's role in sulfate transfer.
• Detection of thiosulfonate reductase activity.

Main Results:

• E. coli extracts contain a sulfotransferase specific for adenosine 3 -phosphate 5 -phosphosulfate.
• Thioredoxin acts as an acceptor molecule for the sulfonyl group, forming organic thiosulfates.
• Thiosulfonate reductase activity was detected, reducing glutathione-S-SO3- to bound sulfide.
• This reductase uses reduced nicotinamide adenine dinucleotide phosphate and Mg2+.

Conclusions:

• Escherichia coli utilizes a sulfate reduction pathway involving bound intermediates, similar to Chlorella.
• A novel sulfotransferase and the role of thioredoxin in this pathway were identified in E. coli.
• The thiosulfonate reductase in E. coli may share activity with sulfite reductase, unlike in Chlorella.