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Localization of arachidonate 12-lipoxygenase in canine brain tissues
M Nishiyama1, H Okamoto, T Watanabe
1Division of Neurosurgery, School of Medicine, Tottori University, Yonago, Japan.
Insights
Canine brain cytosol contains 12-lipoxygenase (12-LO) that converts arachidonic acid to a specific hydroperoxy eicosatetraenoic acid. This brain 12-LO differs from platelet 12-LO in substrate specificity and antibody reactivity.
Area of Science:
- Biochemistry
- Neuroscience
- Enzymology
Background:
- 12-lipoxygenase (12-LO) is an enzyme involved in fatty acid metabolism.
- Understanding the specific forms and functions of 12-LO in different tissues is crucial for elucidating their physiological roles.
Purpose of the Study:
- To characterize the 12-lipoxygenase enzyme present in the canine cerebrum.
- To compare the properties of cerebral 12-LO with that found in canine platelets.
Main Methods:
- Immunoaffinity chromatography using a monoclonal antibody against porcine leukocyte 12-LO.
- Enzyme activity assays with various fatty acid substrates (arachidonic acid, linoleic acid, alpha-linolenic acid).
- Comparison of enzyme properties between canine cerebrum cytosol and canine platelet cytosol.
Main Results:
- Canine cerebrum cytosol contains a 12-lipoxygenase that elutes with some retardation during immunoaffinity chromatography.
- The cerebral enzyme exhibits specific activity of 9 nmol/min/mg protein and converts arachidonic acid to 12(S)-hydroperoxy-5,8,10,14-eicosatetraenoic acid.
- Cerebral 12-LO is active with linoleic and alpha-linolenic acids, unlike canine platelet 12-LO, and shows distinct antibody reactivity.
- 12-Lipoxygenase activity is present in various canine brain regions, including basal ganglia, hippocampus, cerebellum, olfactory bulb, and medulla oblongata.
Conclusions:
- Canine brain cytosol harbors a distinct 12-lipoxygenase isoenzyme.
- This cerebral 12-LO possesses broader substrate specificity compared to its platelet counterpart.
- The presence of 12-LO activity across multiple canine brain regions suggests a significant role in central nervous system function.
Abstract:
The cytosol fraction from a thoroughly irrigated canine cerebrum was subjected to immunoaffinity chromatography using a monoclonal antibody against porcine leukocyte 12-lipoxygenase. Arachidonate 12-lipoxygenase eluted from the column with some retardation. The enzyme, with a specific activity of 9 nmol/min/mg of protein, converted arachidonic acid to 12(S)-hydroperoxy-5,8,10,14-eicosatetraenoic acid. The enzyme was active not only with arachidonic acid, but also with linoleic and alpha-linolenic acids. In contrast, 12-lipoxygenase of canine platelets was almost inactive with linoleic and alpha-linolenic acids, and the platelet enzyme was also distinguished from the cerebral enzyme in terms of reactivity with the anti-12-lipoxygenase antibody. 12-Lipoxygenase activity was also detected in the cytosol fractions of other parts of canine brain: basal ganglia, hippocampus, cerebellum, olfactory bulb, and medulla oblongata.