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PROPERTIES OF RAT BRAIN HISTIDINE DECARBOXYLASE
Author(s) -
Palacios J. M.,
Mengod G.,
Picatoste F.,
Grau M.,
Blanco I.
Publication year - 1976
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.1471-4159.1976.tb02629.x
Subject(s) - histidine , enzyme , chemistry , enzyme assay , substrate (aquarium) , histidine decarboxylase , pyridoxal phosphate , specific activity , biochemistry , phosphate , incubation , cofactor , chromatography , biology , ecology
– The properties of histidine decarboxylase ( l ‐histidine carboxylyase EC 4.1,1.22) have been studied in a whole rat brain homogenate. Optimum pH depended upon substrate concentration; the variations of K m and V max were determined as a function of pH. pH values lower than 6.0 caused a loss of enzymic activity; activity was stable at pH values higher than 6.0. Enzyme activity was proportional to temperature in the range 30‐45°C; temperature characteristic (μ) and Q 10 were determined and thermal inactivation was studied. Addition of pyridoxal 5′‐phosphate increased enzyme activity. Dialysis of homogenates against phosphate buffer caused a partial loss of enzyme activity which could be restored by addition of the coenzyme to the incubation mixture. Enzyme activity was inhibited by α‐methylhistidine and benzene and was unaffected by α‐methyl DOPA. The properties correspond to those of a ‘specific’ histidine decarboxylase. However, the brain enzyme differs from the corresponding enzyme in peripheral tissues in the inability to achieve a total inhibition of activity by dialysis.