Glutamic-oxaloacetic transaminase isozymes in human seminal plasma and sperm extracts.
Leakage of glutamic-oxaloacetic transaminase (GOT) can be used as an indicator of cryo-damage for mammalian spermatozoa. However, two GOT isozymes exist: mitochondrial (m-GOT) and cytosolic or soluble (s-GOT), with acid and alkaline pH optima, respectively. The levels of these GOT isozymes were determined in samples of cell-free human seminal plasma and sperm extracts over a pH range of 3.8 to 9.6. Optimum GOT activities were found at pH 5.2 using cacodylate-HCl buffer (m-GOT) and pH 8.4 using barbital buffer (s-GOT). Differential inhibition studies with adipate (which inhibits s-GOT) were misleading because of the presence of another NADH-linked enzyme able to use adipate as a substrate. Only relatively low levels of m-GOT could be extracted from human spermatozoa (21.4 +/- 31.5 [SD] mU/10(8) cells vs. 202.3 +/- 49.4 mU/mL seminal plasma; n = 20). Consequently, future studies on GOT leakage should be carried out at the alkaline pH optimum, and will therefore measure s-GOT, making this a marker for plasma membrane integrity rather than a measure of mitochondrial damage.
D001219:Aspartate Aminotransferases / Q000378:metabolism*; D002021:Buffers; D002474:Cell-Free System; D003600:Cytosol / Q000201:enzymology; D006801:Humans; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D008297:Male; D008928:Mitochondria / Q000201:enzymology; D012661:Semen / Q000201:enzymology*; D013094:Spermatozoa / Q000201:enzymology*
D002021:Buffers; D001219:Aspartate Aminotransferases