Description_x000D_ General description_x000D_ Pyruvate Kinase from rabbit muscle is a metalloenzyme which catalyzes the conversion of phosphoenol pyruvate to pyruvate in the glycolysis pathway. It corresponds to a molecular weight of 59 kDa. It exists as a tetramer and undergoes conformational changes in the active site to accommodate substrate. Lactic dehydrogenase (LDH) catalyzes the lactate to pyruvate conversion in anaerobic glycolysis. It exists as tetramer and comprises of two subunits (H and M). The LDH of eukaryotes undergo active-site loop gating for their catalytic functionality._x000D_ Application_x000D_ Pyruvate Kinase/Lactic Dehydrogenase enzymes from rabbit muscle has been used:_x000D_ • for ATP generation in the active microtubule preparation_x000D_ • in the enzyme linked ATPase assay of skeletal muscle heavy meromyosin (HMM)_x000D_ • as a standard control for quantifying mesenchymal stem cells (MSCs) lactate dehydrogenase_x000D_ Biochem/physiol Actions_x000D_ ADP Quantification Assay protocol for the use of PK/LDH in the determination of ADP. Solutions containing unkown concentrations of ADP can be substuted for reagent D in this protocol. Further dilutions of the ADP solution may be required_x000D_ Lactate dehydrogenase from rabbit muscle can be inhibited by ascorbate. Aldolase and actin were shown to block this inhibitory effect._x000D_ Pyruvate kinase also catalyzes the phosphorylation of thiamine diphosphate (TDP) to thiamine triphosphate (TTP) which may find application in antiviral and tumor therapy._x000D_ Pyruvate kinase requires bivalent and monovalent cations such as Mg2+ and K+ respectively for activation to occur._x000D_ Unit Definition_x000D_ Pyruvate kinase activity: One unit will convert 1.0 μmole of phospho(enol)pyruvate to pyruvate per min at pH 7.6 at 37 °C._x000D_ Lactic dehydrogenase activity: One unit will reduce 1.0 μmole of pyruvate to L-lactate per min at pH 7.5 at 37 °C._x000D_ Physical form_x000D_ Solution in 50% glycerol containing 10 mM HEPES, pH 7.0, 100 mM KCl and 0.1 mM EDTA