The activity of six hydrolytic enzymescarboxyl esterase, acid phosphatase, alkaline phosphatase, b-galactosidase, b-glucosidase and b-hexosaminidase, were studied in different regions of the normal human brain tissue obtained at autopsy. Protein estimation and activities of the hydrolytic enzymes with respective substrates were assayed by spectrophotometric and spectroflourometric methods. Amongst the eight regions of the brain-frontal, parietal, occipital, temporal, thalamus, cerebellum and hippocampus, the pineal gland showed highest activity for all hydrolytic enzymes studied except for carboxyl esterase. Among six hydrolases studied, hexosaminidase exhibited highest activity in all regions of the human brain while alkaline phosphatase activity was the least amongst all regions studied. A majority of the enzymes studied showed higher activity in gray matter as compared to the white matter except acid phosphatase and b-glucosidase which exhibited higher activity in the white matter. The most significant finding in the present study was the high activity of all hydrolytic enzymes noted in the pineal gland as compared to all other regions of the human brain. Such a finding has not been hitherto reported earlier in human brain tissue samples. If the specific activities of these enzymes are to be considered as any functional index, then pineal gland may be more metabolically active tissue with respect to the hydrolytic function as compared to the other regions of the brain.

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