Premium
Effects of Phospholipases on the Kinetic Properties of Rat Striatal Membrane‐Bound Tyrosine Hydroxylase
Author(s) -
Kuczenski Ronald
Publication year - 1983
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1983.tb08053.x
Subject(s) - tyrosine 3 monooxygenase , tyrosine hydroxylase , tyrosine , enzyme , phospholipase a2 , biochemistry , chemistry , phospholipase a , cofactor , phospholipase , biology
Rat striatal tyrosine hydroxylase can be isolated in both a soluble and a synaptic membrane‐bound form. The membrane‐bound enzyme, which exhibits lower K m s for both tyrosine (7 μ M ) and reduced pterin cofactor (110 μ M ) relative to the soluble enzyme (47 μ M and 940 μ M , respectively), can be released from the membrane fraction with mild detergent, and concomitantly its kinetic properties revert to those of the soluble enzyme. Treatment of membrane‐bound tyrosine hydroxylase with C. perfringens phospholipase C increased the K m of the enzyme for tyrosine to 27 μ M and the V max by 60% without changing the K m for cofactor. In contrast, treatment of membrane‐bound tyrosine hydroxylase with V. russelli phospholipase A 2 increased the K m for tyrosine to 48 μ M increased the V max and increased the K m for cofactor to 560 μ M . The enzyme remained bound to the membrane fraction following both phospholipase treatments. Addition of phospholipids to treated enzyme could partially reverse the effects of phospholipase A 2 treatment, but not the effects of phospholipase C treatment. The kinetic properties of phospholipase‐treated, detergent‐solubilized tyrosine hydroxylase were identical to those of the control solubilized enzyme. Tyrosine hydroxylase appears to interact with synaptic membrane components to produce at least two separately determined consequences for the kinetic properties of the enzyme.