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Properties and Ontogenic Development of Membrane‐Bound Histidine Decarboxylase from Rat Brain
Author(s) -
Toledo A.,
Sabriá J.,
Rodriguez R.,
Brandner R.,
Rodriguez J.,
Palacios J. M.,
Blanco I.
Publication year - 1988
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.1471-4159.1988.tb01104.x
Subject(s) - membrane , histidine , enzyme , chemistry , biochemistry , specific activity , substrate (aquarium) , pyridoxal phosphate , pyridoxal , enzyme assay , phosphate , histidine decarboxylase , cofactor , chromatography , biology , ecology
Histidine decarboxylase (HD) activity was determined in high‐speed fractions (100,000 g for 60 min) obtained from whole rat brain homogenates. Twenty‐eight percent of the HD activity was associated with membranes, and the remaining was soluble. Several properties of the soluble and membrane‐bound HD were compared. No significant differences in the values of K m for histidine and pyridoxal 5′‐phosphate were observed. The solubilization of membrane‐bound HD with Triton X‐100 resulted in an increase of 60% over the nonsolubilized activity with no changes in the K m for substrate and cofactor. The proportion of free pyridoxal 5′‐phosphate‐independent activity was identical in both fractions. The soluble and membrane‐bound forms of the enzyme differ slightly in their pH‐activity profiles, although both enzymes showed an optimum pH near 6.5. The HD activities present in soluble and membrane fractions were determined at different postnatal ages. The soluble activity increased until day 90, whereas the membrane‐bound activity became stabilized from day 20.