Rate-limiting step of purine and pyrimidine synth

[Dnestr]

According to rapid review biochemistry, the rate-limiting steps of purine and pyrimidine are PRPP synthetase and CPS II, respectively. First Aid says that it's Glutamine-PRPP amidotransferase and aspartate transcarbamylse, respectively.

Anyone have any thoughts?

Sorry if this was already posted.

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[gouda]

FA has the prokaryotic rate limiting step for pyrimidine synthesis (asp. trans.) listed...in eukaryotes it is CPSII.

I don't know how to answer the purine thing because there is discrepancy in the literature, but if you know the first two enzyme in purine syn (PRPP syn and Glut...) then you'll be fine.

I found the whole switch between eukaryotes and prokaryotes irritating in the biochem section because they never said when they were talking about one or the other (ie - the DNA replication is all prokaryotic in FA, but other sources highlight eukaryotic...just know both for the test)

 

[Dnestr]

Thanks.... that clears it up. That eukaryotic/prokaryotic switch is pretty obnoxious.

 

[DoctaJay]

I agree. Thanks alot for clearing that up.

 

[Glaxo]

what's the RLS for purine synthesis?? goljan book says PRPP synthase first aid says glutamine PRPP amido transferase I'm assuming that since it's got all the feed back. Thanks

 

[ENThopeful]

FA has the prokaryotic rate limiting step for pyrimidine synthesis (asp. trans.) listed...in eukaryotes it is CPSII.

I don't know how to answer the purine thing because there is discrepancy in the literature, but if you know the first two enzyme in purine syn (PRPP syn and Glut...) then you'll be fine.

I found the whole switch between eukaryotes and prokaryotes irritating in the biochem section because they never said when they were talking about one or the other (ie - the DNA replication is all prokaryotic in FA, but other sources highlight eukaryotic...just know both for the test)

.