Purified cortical neurons and cerebellar granular neurones had no aspartoacylase activity. Primary O-2A progenitor cells had moderate activity (0.136 ± 0.073 nmol/min/mg protein) with approximately three fold higher activity in immature oligodendrocytes (0.341 ± 0.137 nmol/min/mg protein) and 13 fold higher levels in mature oligodendrocytes (1.749 ± 0.261 nmol/min/mg protein). However, the highest activity (20 fold) was seen in type-2 astrocytes (2.832 ± 0.785 nmol/min/mg protein) derived from the same source. Type-1 astrocytes had lower levels of aspartoacylase activity then those seen in mature oligodendrocytes (0.136 ± 0.073 nmol/min/mg protein).
Aspartoacylase activity was absent from freshly isolated astrocytes; however, there was an induction of enzyme activity in culture over time with significantly higher activity after 14 days in culture (see Figure 6).
Fig 6. Aspartoacylase activity in Astrocytes
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