Characterization of the isoenzyme profile of beta-N-acetylhexosaminidase in the urine of newborns

The urinary isoenzymes of beta-N-acetylhexosaminidase (Hex) in newborn infa nts were characterised by chromatography, electrophoresis, thermodynamic an alysis and through substrate specificity. No qualitative difference was fou nd for the major Hex A and Hex B isoenzymes between full-term or premature newborns and adults, although in the latter group the relative proportion o f Hex B is much lower (18.5 +/- 2.7 % vs. 36.3 +/- 1.0 %). An additional mi nor enzyme form was found in some premature newborns, which eluted from the DEAE-cellulose column at a higher concentration of NaCl than Hex A and, li ke this isoenzyme, is able to hydrolyse 4-methylumbellipheryl-2-acetamido-2 -deoxP-D-glucopyranoside-6-sulphate, which would suggest that it has alpha subunits in its molecule. These results do not confirm the hypothesis of ot her authors about the existence of a unique fetal Hex isoenzyme in neonatal urine which eluted before the application of the NaCl gradient, similarly to the Hex B.