Phosphorylation of Threonine 107 by Calcium/Calmodulin dependent Kinase II δ Regulates the Detoxification Efficiency and Proteomic Integrity of Glyoxalase 1
The glyoxalase system is a ubiquitously expressed enzyme system with narrow substrate specificity and is responsible for the detoxification of harmful methylglyoxal (MG), a spontaneous by-product of energy metabolism. Glyoxalase 1 (Glo1) is the first and therefore rate limiting enzyme of this protective system. In this study we were able to show that a phosphorylation of threonine-107 in the Glo1 protein, mediated by Ca2+/Calmodulin-dependent Kinase II delta (CamKII{delta}), is associated with elevated catalytic efficiency of Glo1. In fact, Michaelis-Menten kinetics of Glo1 mutants revealed that a permanent phosphorylation of Glo1 was associated with increased Vmax (1.23 {micro}mol/min/mg) and decreased Km (0.19 mM HTA), whereas the non-phosphorylatable Glo1 showed significantly lower Vmax (0.66 {micro}mol/min/mg) and increased Km (0.31 mM HTA). This was also confirmed with human recombinant Glo1 (Vmax (Glo1phos) = 999 {micro}mol/min/mg; Km (Glo1phos) = 0.09 mM HTA vs. Vmax (Glo1red) = 497 {micro}mol/min/mg; Km (Glo1red) = 0.12 mM HTA). Additionally, proteasomal degradation of non-phosphorylated Glo1 via ubiquitination occurred more rapidly as compared to native Glo1. The absence of the responsible kinase CamKII{delta} was associated with poor MG detoxification capacity and decreased protein content of Glo1 in a murine CamKII{delta} knock-out model. Furthermore, this regulatory mechanism is also related to an altered Glo1 status in cancer, diabetes and during aging. In summary, phosphorylation of threonine-107 in the Glo1 protein by CamKII{delta} is a quick and precise mechanism regulating Glo1 activity.