J. Biol. Chem., Vol. 262, Issue 12, 5654-5658, Apr, 1987
Interaction of cytoplasmic tyrosine hydroxylase with chromaffin granule. In vitro studies on association of soluble enzyme with granule membranes and alteration in enzyme activity
K Morita, K Teraoka and M Oka
The interaction of soluble tyrosine hydroxylase with isolated chromaffin
granule membranes was studied. The incubation of the granule membranes with
the soluble fraction in the mixture that may approximate the intracellular
environment of the resting cell resulted in a marked increase in the enzyme
activity recovered in the membrane fraction, and enzyme activity
precipitated with the granule membranes was increased according to
incubation time and dependent on amounts of both the granule membranes and
soluble fraction. The association of the soluble enzyme with the granule
membranes was reversible and specific, whereas a decrease in activity of
the soluble enzyme was observed when the soluble fraction was incubated
with the granule membranes in the mixture in which association of the
soluble enzyme with the granule membranes might occur. These results seem
to indicate that activity of the soluble enzyme is presumably modulated by
the granule through association of the soluble enzyme with the surface of
the granule, thus suggesting that interaction between tyrosine hydroxylase
and the chromaffin granule may play a possible role in regulation of
catecholamine biosynthesis as a consequence of modulating activity of the
rate-limiting enzyme within the cell.
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