Source:http://biocyc.org/biopax/biopax-level3Catalysis159514
| Predicate | Object |
|---|---|
| rdf:type | |
| biopax3:controlType |
ACTIVATION
|
| biopax3:controlled | |
| biopax3:cofactor | |
| biopax3:comment |
Hypoxanthine-guanine phosphoribosyltransferase catalyzes the |FRAME: MG+2|-dependent synthesis of |FRAME: IMP| and |FRAME: GMP| by addition of the 6-oxopurine bases |FRAME: HYPOXANTHINE|, or |FRAME: GUANINE|, respectively to the 1-β position of |FRAME: PRPP|. In this sequential reaction, |FRAME: PRPP| binds to the free enzyme before the purine base. Following covalent coupling, |FRAME: PPI| is released before the purine nucleoside monophosphate (in |CITS: [15990111]|). The detailed sequential kinetic mechanism has been studied in both the forward (favored) and reverse directions using the human recombinant enzyme. Product release is the rate-limiting catalytic step |CITS: [9132023]|. The purified human brain enzyme had <i>K</i><sub>m</sub> values for |FRAME: HYPOXANTHINE| and |FRAME: PRPP| of 50 μM and 111 μM, respectively. |FRAME: GMP| and |FRAME: IMP| competitively inhibited with respect to |FRAME: PRPP|, but not |FRAME: HYPOXANTHINE| |CITS: [3091416]|. Unpurified recombinant enzyme expressed in <i>Escherichia coli</i> was compared with unpurified enzyme from erythrocytes and lymphoblasts. The <i>K</i><sub>m</sub> values for |FRAME: GUANINE| were similar, but those for |FRAME: PRPP| differed significantly in the case of the erythrocyte enzyme, possibly due to oxidation of the preparation |CITS: [2223882]|.
|
| biopax3:xref | |
| biopax3:controller | |
| biopax3:dataSource | |
| biopax3:displayName |
hypoxanthine phosphoribosyltransferase
|
| biopax3:evidence | |
| biopax3:standardName |
hypoxanthine phosphoribosyltransferase
|