Properties of glutaminase of crayfish CNS: implications for axon–glia signaling

Glutaminase of crayfish axons is believed to participate in recycling of axon–glia signaling agent(s). We measured the activity and properties of glutaminase in crude homogenates of crayfish CNS, using ion exchange chromatography to separate radiolabeled product from substrate. Crayfish glutaminase...

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Published in:	Neuroscience Vol. 114; no. 3; pp. 699 - 705
Main Authors:	Engler, J.A, Gottesman, J.M, Harkins, J.C, Urazaev, A.K, Lieberman, E.M, Grossfeld, R.M
Format:	Journal Article
Language:	English
Published:	Oxford Elsevier Ltd 01-01-2002 Elsevier
Subjects:	Animals Astacidea Astacoidea - enzymology Axons - drug effects Axons - enzymology Biochemistry. Physiology. Immunology Biological and medical sciences Central Nervous System - drug effects Central Nervous System - enzymology Crustacea Fundamental and applied biological sciences. Psychology glutamate Glutaminase - antagonists & inhibitors Glutaminase - metabolism glutamine Invertebrates N-acetylaspartylglutamate Neuroglia - drug effects Neuroglia - enzymology Physiology. Development Signal Transduction - drug effects Signal Transduction - physiology N-acetylaspartylglutamate DON, 6-diazo-5-oxo- L-norleucine NCS, normal (physiological) saline PAG, phosphate-activated glutaminase GAD, glutamate decarboxylase PIG, phosphate-independent glutaminase glutamine glutamate NAAG, N-acetylaspartylglutamate Glial cell Enzyme Neuroglia Central nervous system Axon Glutamate Glutaminase Macrura Crustacea Arthropoda Excitatory aminoacid Neurotransmitter Hydrolases Decapoda Procambarus clarkii Invertebrata Glutamine
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Summary:	Glutaminase of crayfish axons is believed to participate in recycling of axon–glia signaling agent(s). We measured the activity and properties of glutaminase in crude homogenates of crayfish CNS, using ion exchange chromatography to separate radiolabeled product from substrate. Crayfish glutaminase activity is cytoplasmic and/or weakly bound to membranes and dependent on time, tissue protein, and glutamine concentration. It resembles the kidney-type phosphate-activated glutaminase of mammals in being stimulated by inorganic phosphate and alkaline pH and inhibited by the product glutamate and by the glutamine analog 6-diazo-5-oxo- L-norleucine. During incubation of crayfish CNS fibers in Na +-free saline containing radiolabeled glutamine, there is an increased formation of radiolabeled glutamate in axoplasm that is temporally associated with an increase in axonal pH from about 7.1 to about 8.0. Both the formation of glutamate and the change in pH are reduced by 6-diazo-5-oxo- L-norleucine. Our results suggest that crayfish glutaminase activity is regulated by cellular changes in pH and glutamate concentration. Such changes could impact availability of the axon–glia signaling agents glutamate and N-acetylaspartylglutamate.
Bibliography:	ObjectType-Article-2 SourceType-Scholarly Journals-1 ObjectType-Feature-1 content type line 23 ObjectType-Article-1 ObjectType-Feature-2
ISSN:	0306-4522 1873-7544
DOI:	10.1016/S0306-4522(02)00357-3