4mb1
The Structure of MalL mutant enzyme G202P from Bacillus subtilusThe Structure of MalL mutant enzyme G202P from Bacillus subtilus
Structural highlights
Function[O16G1_BACSU] Hydrolyzes various disaccharides such as sucrose, maltose, and isomaltose with different efficiencies. Also hydrolyzes longer maltodextrins from maltotriose up to maltohexaose, but not maltoheptaose, palatinose, isomaltotriose, or isomaltotetraose. Publication Abstract from PubMedThe increase in enzymatic rates with temperature up to an optimum temperature (Topt) is widely attributed to classical Arrhenius behavior, with the decrease in enzymatic rates above Topt ascribed to protein denaturation and/or aggregation. This account persists despite many investigators noting that denaturation is insufficient to explain the decline in enzymatic rates above Topt. Here we show that it is the change in heat capacity associated with enzyme catalysis (DeltaCdouble daggerp) and its effect on the temperature dependence of DeltaGdouble dagger that determines the temperature dependence of enzyme activity. Through mutagenesis, we demonstrate that the Topt of an enzyme is correlated with DeltaCdouble daggerp and that changes to DeltaCdouble daggerp are sufficient to change Topt without affecting the catalytic rate. Furthermore, using X-ray crystallography and molecular dynamics simulations we reveal the molecular details underpinning these changes in DeltaCdouble daggerp. The influence of DeltaCdouble daggerp on enzymatic rates has implications for the temperature dependence of biological rates from enzymes to ecosystems. Change in Heat Capacity for Enzyme Catalysis Determines Temperature Dependence of Enzyme Catalyzed Rates.,Hobbs JK, Jiao W, Easter AD, Parker EJ, Schipper LA, Arcus VL ACS Chem Biol. 2013 Sep 17. PMID:24015933[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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