Lesson plan
Multienzyme complex
In molecular biology, a multienzyme complex is a protein complex containing several copies of one or more enzymes packed into one macromolecular assembly. Multienzyme complexes carry out a single or multi-step biochemical reaction taking place within cells. It allows the cell to segregate certain biochemical pathways into one place in the cell. Examples include pyruvate dehydrogenase, fatty acid synthetase, glutamine synthetase, proteasome, rubisco. A multienzyme complex that functions in the histidine biosynthesis pathway has been studied at the biochemical and genetic level in the fungus Neurospora crassa. A gene (His-3) was found to encode a protein that functions as a multienzyme complex having three distinct enzymatic activities in the biosynthesis pathway. A genetic analysis of mutants defective in the N. crassa histidine pathway indicated that the individual activities of the multienzyme complex occur in discrete regions of the His-3 genetic map. This finding suggested that each of the activities of the multienzyme complex are encoded separately from each other, but within the same gene. Some His-3 mutants were also found that lacked all three activities simultaneously, suggesting that some mutations can cause loss of function of the whole multienzyme complex.
Article summary
In molecular biology, a multienzyme complex is a protein complex containing several copies of one or more enzymes packed into one macromolecular assembly. Multienzyme complexes carry out a single or multi-step biochemical reaction taking place within cells. It allows the cell to segregate certain biochemical pathways into one place in the cell. Examples include pyruvate dehydrogenase, fatty acid synthetase, glutamine synthetase, proteasome, rubisco. A multienzyme complex that functions in the histidine biosynthesis pathway has been studied at the biochemical and genetic level in the fungus Neurospora crassa. A gene (His-3) was found to encode a protein that functions as a multienzyme complex having three distinct enzymatic activities in the biosynthesis pathway. A genetic analysis of mutants defective in the N. crassa histidine pathway indicated that the individual activities of the multienzyme complex occur in discrete regions of the His-3 genetic map. This finding suggested that each of the activities of the multienzyme complex are encoded separately from each other, but within the same gene. Some His-3 mutants were also found that lacked all three activities simultaneously, suggesting that some mutations can cause loss of function of the whole multienzyme complex.
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Discussion questions
- Summarise the article in your own words. Which single claim would you verify first, and why?
- Which claim in this article is most likely to be revised as the sources update? How would you check its current status?
- If two sources disagreed about one of these facts, what would you need in order to trust one over the other?
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