(Clinical Chemistry. 1998;44:226-231.)
© 1998 American Association for Clinical Chemistry, Inc.
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Enzymes and Protein Markers |
Assay of ß-N-acetylhexosaminidase isoenzymes in different biological specimens by means of determination of their activation energies
Luis F. Pérez,
and J. Carlos Tutora
a Author for correspondence. Fax Int + 34-81-57 01 02.
The activation energy (Ea) of
ß-N-acetylhexosaminidase (Hex, EC 3.2.1.52) was
determined with
3,3'-dichlorophenylsulfonphthaleinyl-N-acetyl-ß-D-glucosaminide
as substrate, with a much higher value being found for the Hex B
isoenzyme (Ea = 75.1 kJ/mol) than for the Hex A isoenzyme
(Ea = 41.8 kJ/mol). This fact allowed for the development
of a fast and reliable thermodynamic method to determine the isoenzyme
composition of Hex in different biological specimens (serum/plasma,
saliva, cerebrospinal fluid, seminal plasma, urine, and leukocyte
lysates). The results in serum given by the proposed method may be
superimposed upon those obtained by the heat inactivation assay of
O'Brien et al. (N Engl J Med 1970;273:15–20), and the
catalytic activity calculated for Hex A offers a good correlation with
that obtained by using the specific substrate
4-methylumbelliferyl-N-acetyl-ß-D-glucosaminide-6
sulfate (n = 25, r = 0.953).
