CHEM 445 / BIOL 445
Biochemistry II

J. D. Cronk
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32. header

Lecture 32. Purine biosynthesis

Wednesday 18 April 2007

Hypoxanthine-guanine phosphoribosyltransferase (HGPRT) and the purine salvage pathway. A de novo purine biosynthetic pathway begins with phosphoribosyl pyrophosphate (PRPP), with the rest of the purine ring structure built up in a stepwise manner. This produces inosine monophosphate (inosinate, IMP). Adenylate and guanylate are produced from IMP. Purine catabolism. Disorders in nucleotide metabolism: SCID, gout, Lesch-Nyhan Syndrome.

Reading: BTS6, Ch.25, pp.714-718, 725-727.

 
25. Summary

Lecture 32 Summary

Hypoxanthine phosphoribosyltransferase (also called hypoxanthine-guanine phosphoribosyltransferase HGPRT, [EC 2.4.2.8] and the purine salvage pathway. Another salvage enzyme: Adenine phosphoribosyltransferase. [EC 2.4.2.7]

A de novo purine biosynthetic pathway begins with phosphoribosyl pyrophosphate (PRPP) as a substrate for amidophosphoribosyltransferase [EC 2.4.2.14] (the book calls this glutamine phosphoribosyl amidotransferase - BTS6, p.714, bottom). The rest of the purine ring structure is built up stepwise by the addition of glycine, the formyl group from N10-formyltetrahydrofolate, and another amino group from glutamine, bicarbonate, the a-amino group from aspartate, and finally another formyl group from N10-formyltetrahydrofolate. This produces inosine monophosphate (inosinate, IMP).Adenylate and guanylate are produced from IMP .

 

 

Disorders in nucleotide metabolism: SCID, gout, Lesch-Nyhan Syndrome.

High serum levels of urate is a risk factor for gout

Purine catabolism

Nucleotidase

Adenosine deaminase

Study questions

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Page updated 12-27-06

References

1. Berg, Tymoczko, and Stryer. Biochemistry (BTS): 6th edition (2007, Freeman) Ch.25, pp.714-718, 725-727.
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