Thermodynamic study of beta-N-acetylhexosaminidase enzyme heterogeneity in human seminal plasma.
BACKGROUND
It has been suggested that the activity of beta-N-acetylhexosaminidase (Hex) in seminal plasma may be used as a biochemical marker of azoospermia. The purpose of our study was to evaluate this hypothesis using a thermodynamic procedure developed to determine total Hex activity and that of its isoenzymes in this biological fluid.


METHODS
Using the substrate 3,3'-dichlorophenolsulphoftaleinil N-acetyl-beta-D-glucosaminide, a highly significant difference (p<0.001) is found between the activation energy of Hex A (41.5 kJ/mol) and of Hex B (72.3 kJ/mol), making it possible to determine the activity of these isoenzymes from the apparent activation energy of the total Hex in seminal plasma.


RESULTS
A significant difference between the normozoospermic and azoospermic groups was only found for Hex A isoenzyme activity (p<0.05), although with considerable overlapping between the values of both groups. Significant partial correlations were found for the total Hex, Hex A and Hex B activities with the immobile spermatozoa count (p<0.01) and for total Hex and Hex B with the dead spermatozoa count (p<0.05). In turn, Hex A had a significant partial correlation with the live spermatozoa count (p<0.05); however, Hex activity in seminal plasma of acromosomal origin appears to be of little importance in quantitative terms.


CONCLUSIONS
It was not possible to confirm that total Hex activity in seminal plasma, or even of its isoenzymes Hex A and Hex B, is a suitable biochemical marker of azoospermia (efficiency< or =67%). The thermodynamic procedure described may be a useful alternative for the study of the Hex enzyme heterogeneity in spermatozoa.
Casal
J Antonio
JA
Laboratorio Central, Hospital Clínico Universitario, 15706 Santiago de Compostela, Spain.
Vizcaíno
Luis
L
Garcia-Devesa
Jesús
J
Tutor
J Carlos
JC
D000328:Adult; D004789:Enzyme Activation; D054818:Hexosaminidase A; D054819:Hexosaminidase B; D006801:Humans; D007527:Isoenzymes; D008297:Male; D008875:Middle Aged; D009845:Oligospermia / Q000201:enzymology; D012661:Semen / Q000201:enzymology*; D013816:Thermodynamics; D014659:Vasectomy; D001619:beta-N-Acetylhexosaminidases / Q000737:chemistry* / Q000378:metabolism*
D007527:Isoenzymes; D054818:Hexosaminidase A; D054819:Hexosaminidase B; D001619:beta-N-Acetylhexosaminidases