Kinetic characterization of lactate dehydrogenase in normal and malignant human breast tissues

Abstract

BackgroundAerobic glycolysis rate is higher in breast cancer tissues than adjacent normal tissues which providethe ATP, lactate and anabolic precursors required for tumourgenesis and metastasis. Lactate dehydrogenase (LDH) is a critical enzyme during aerobic glycolysis as it is typically responsible for the production of lactate and regeneration of NAD+, which allows for the continued functioning of glycolysis even in the absence of oxygen. LDH has been found to be highly expressed in breast tumors. Enzyme kinetic characteristics is related to environmentinvolving the enzyme, and tumor microenvironment has distinct features relative to adjacent normal tissues, thus we hypothesized that LDH should have different kinetic characteristics in breast tumors compared to normal breast tissues.MethodsLDH was partially purifiedfrom human breast tumors and normal tissues, which were obtained directly from operating room. TheMichaelis-Menten constant (Km), maximum velocity (Vmax), activation energy (Ea) and enzyme efficiency in breast tumors and normal tissueswere determined.ResultsIt was found that tumor LDH affinity in forward reaction was the same as normal LDH but Vmax of cancerous LDH was higher relative to normal LDH. In reverse reaction, affinity of tumor LDH for lactate and NAD+ was lower than normal LDH, also enzyme efficiency for lactate and NAD+ was higher in normal samples. The Ea of reverse reaction was higher in cancerous tissues.ConclusionsIt was concluded that thelow LDH affinity for lactate and NAD+ is a valuable tool for preserving lactate by cancer cells. We also conclude that increasing of LDH affinity may be a valid molecular target to abolish lactate dependent tumor growth and kinetic characteristics of LDH could be a novel diagnostic parameter for human breast cancer.

Metabolic and oncogenic adaptations to pyruvate dehydrogenase inactivation in fibroblasts

“…An alternative use of oxaloacetate, namely in gluconeogenesis, seems unlikely given the high rates of cell growth, the high glucose content of the cell culture medium used in these studies, and the fact that fibroblast gluconeogenesis is typically low (69,70). In addition to feedback inhibition of lactate dehydrogenase (LDH) by pyruvate and lactate (81), pyruvate carboxylase's 10 -30-fold lower K m value for pyruvate may also play a role (82)(83)(84)(85).…”

An antioxidant activity of Cinnamonum tamala improves histopathological alterations and biochemical parameters in alloxan induced diabetic rats

“…Lactate dehydrogenase (LDH) is the enzyme that helps to catalyze the interconversion of pyruvate to lactate and viceversa in the glycolysis process. 46 Increased level of LDH activity in diabetic rats is linked with less insulin availability in diabetes. However, treatment with extract decreases the activity of LDH may be because this extract controls the amount of pyruvate and NADH, thus it helps to process oxidation of glucose in mitochondria.…”

Chiral Pyridine-3,5-bis- (L-phenylalaninyl-L-leucinyl) Schiff Base Peptides as Potential Anticancer Agents: Design, Synthesis, and Molecular Docking Studies Targeting Lactate Dehydrogenase-A

“…It is clear that cancer cells mainly produce energy through glycolysis and LDHA is the final enzyme involved in this pathway [26]. As LDHA is a vital supporter of glucose metabolism in cancer cells and its increased level is a marker for many tumors, LDHA can be defined as an anticancer drug target [27]. Previous literatures reported that V-shape structures illustrate good LDHA inhibition, so molecular modification of the potentially identified LDHA inhibitors A-C ( Figure 1) might provide more effective hits [28][29][30].…”