Inositol Monophosphatase: Difference between revisions
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=Function= | =Function= | ||
===IMPase=== | ===IMPase=== | ||
IMPase activity within ''M. jannaschii'' is mainly limited to the production pathway of a unique inositol, di-''myo''-inositol-1,1'-phosphate (DIP), using DL-''myo''-inositol-1-phosphate as substrate. Intracellular DIP concentrations increase usually in response to supraoptimal growth temperatures, and is involved in maintaining high cellular concentration of K+ which sustains optimal enzyme activity<ref>PMID: 9683472</ref>. IMPase | IMPase activity within ''M. jannaschii'' is mainly limited to the production pathway of a unique inositol, di-''myo''-inositol-1,1'-phosphate (DIP), using DL-''myo''-inositol-1-phosphate as substrate. Intracellular DIP concentrations increase usually in response to supraoptimal growth temperatures, and is involved in maintaining high cellular concentration of K+ which sustains optimal enzyme activity<ref>PMID: 9683472</ref>. IMPase K<sub>m</sub> and K<sub>cat</sub> at 85°C; 91±16μM and 4.2±0.2/s, respectively<ref name="rasmol"/>. | ||
===FBPase=== | ===FBPase=== | ||
Under normal conditions the MJ0109 gene product preferentially metabolizes the second last major step in [http://en.wikipedia.org/wiki/Gluconeogenesis| gluconeogenesis], fructose-1,6-bisphosphate substrate to fructose-6-phosphate. Relative to its IMPase activity, the FBPase activity of MJ0109 is 1.63 times as active<ref name="rasmol"/>. This particular function was not immediately identified by genomic sequence alignment and was later determined using structual and kinetic analysis<ref name="rasmol"/>. FBPase | Under normal conditions the MJ0109 gene product preferentially metabolizes the second last major step in [http://en.wikipedia.org/wiki/Gluconeogenesis| gluconeogenesis], fructose-1,6-bisphosphate substrate to fructose-6-phosphate. Relative to its IMPase activity, the FBPase activity of MJ0109 is 1.63 times as active<ref name="rasmol"/>. This particular function was not immediately identified by genomic sequence alignment and was later determined using structual and kinetic analysis<ref name="rasmol"/>. FBPase K<sub>m</sub> and K<sub>cat</sub> at 85°C; 38±9μM and 7.0±0.4/s, respectively<ref name="rasmol"/>. | ||
===Inhibitors=== | ===Inhibitors=== | ||
As the dual activity indicates, the substrate specificity of this enzyme is particularly low. Proposed evolutionary cousins of this enzyme are regulated by [http://en.wikipedia.org/wiki/Adenosine_monophosphate| Adenosine monophosphate] and [http://en.wikipedia.org/wiki/Fructose_2,6-bisphosphate| Fructose 2,6-bisphosphate]. However, there are no such allosteric regulatory binding sites on the MJ0109 protein. Additionally, ''M. jannaschii'' IMPase has a [http://en.wikipedia.org/wiki/IC50| IC50] for Li+ of >150mM, compared to the Li+ IC50 of human IMPase <1mM<ref name="rasmol"/>. | As the dual activity indicates, the substrate specificity of this enzyme is particularly low. Proposed evolutionary cousins of this enzyme are regulated by [http://en.wikipedia.org/wiki/Adenosine_monophosphate| Adenosine monophosphate] and [http://en.wikipedia.org/wiki/Fructose_2,6-bisphosphate| Fructose 2,6-bisphosphate]. However, there are no such allosteric regulatory binding sites on the MJ0109 protein. Additionally, ''M. jannaschii'' IMPase has a [http://en.wikipedia.org/wiki/IC50| IC50] for Li+ of >150mM, compared to the Li+ IC50 of human IMPase <1mM<ref name="rasmol"/>. | ||
