Figure 2.
Role of lactate dehydrogenase as a supplier of NADH for bull sperm capacitation. Cytosolic and mitochondrial LDHC4 are important to supply NADH for the sperm oxidase that produces extracellular O2•– for bull sperm capacitation. Lactate is converted by the LDH-C4cyt into pyruvate and NADH that will be used as oxidases for capacitation. The pyruvate will enter into the mitochondrion to be converted into acetyl-CoA and enter into the Krebs cycle. Then, reducing equivalents will be transferred to the respiratory chain to produce ATP that will be used for energy purposes and to provide phosphate groups for a series of phosphorylation events. AC: adenylyl cyclase; PLC: phospholipase C; PKA: protein kinase A; PKC: protein kinase C; PTK: protein tyrosine kinase; O2•–: superoxide anion; LDH-C4cyt: cytosolic lactate dehydrogenase-C4.