S. Murphy et A. Pastuszko, EFFECT OF NEUROCATIN ON THE ACTIVITY OF MONOAMINE-OXIDASE-B IN BAT BRAIN SYNAPTOSOMES, Neurochemical research, 19(2), 1994, pp. 177-182
Neurocatin, a small (about 2,000 Dalton) neuroregulator isolated from
mammalian brain, is a powerful effector of monoamine oxidase B in rat
brain synaptosomes. Incubation of intact synaptosomes with neurocatin
caused an inhibition of the enzyme dependent on the concentration of n
eurocatin. This inhibition became statistically significant at a neuro
catin concentration of 10 ngl 200 mu l and was significant at all high
er neurocatin concentrations. At 40 ng/200 mu l, neurocatin inhibited
monoamine oxidase B activity by about 60%. This inhibitory effect was
almost completely abolished by breaking the synaptosomal membrane by h
ypotonic buffer prior to incubation with neurocatin. In addition, incu
bation of the synaptosomes in calcium free medium almost completely ab
olished the inhibitory effect of neurocatin On monoamine oxidase B. Th
e inhibition appeared to involve covalent modification of the enzyme m
ediated by a neurocatin receptor(s). Measurements of the kinetic param
eters of the enzyme showed that 20 ng of neurocatin caused a statistic
ally significant decrease in V-max (by 20%) with no significant change
in K-M, compared to controls. Inhibition of monoamine oxidase by neur
ocatin is potentially of great clinical importance because this enzyme
plays a major role in catabolism of the biogenic amines and alteratio
ns in its activity is believed to contribute to several neurological d
isorders.