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 Ca 2+ /Calmodulin-dependent Kinase II delta (CamKIIδ), 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 V max (1.23 µmol/min/mg) and decreased K m (0.19 mM HTA), whereas the non-phosphorylatable Glo1 showed significantly lower V max (0.66 µmol/min/mg) and increased K m (0.31 mM HTA). This was also confirmed with human recombinant Glo1 (V max (Glo1 phos ) = 999 µmol/min/mg; K m (Glo1 phos ) = 0.09 mM HTA vs. V max (Glo1 red ) = 497 µmol/min/mg; K m (Glo1 red ) = 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 CamKIIδ was associated with poor MG detoxification capacity and decreased protein content of Glo1 in a murine CamKIIδ 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 CamKIIδ is a quick and precise mechanism regulating Glo1 activity.