Compartmentation of glutamate metabolism in brain. Evidence for the existence of two different tricarboxylic acid cycles in brain

• Published in: Biochemical journal Vol. 113; no. 2; pp. 281 - 290
• Main Authors: Van den Berg, C J, Krzalić, L, Mela, P, Waelsch, H
• Format: Journal Article
• Language: English
• Published: England 01.06.1969
• Subjects: Acetates - metabolism; Animals; Aspartic Acid - metabolism; Brain - metabolism; Carbon Isotopes; Citric Acid Cycle; Glucose - metabolism; Glutamates - metabolism; Glutamine - metabolism; Mice; Models, Chemical
• ISSN: 0264-6021; 0306-3283; 1470-8728
• DOI: 10.1042/bj1130281

1. (14)C from [1-(14)C]glucose injected intraperitoneally into mice is incorporated into glutamate, aspartate and glutamine in the brain to a much greater extent than (14)C from [2-(14)C]glucose. This difference for [1-(14)C]glucose and [2-(14)C]glucose increases with time. The amount of (14)C in C-1 of glutamate increases steadily with time with both precursors. It is suggested that a large part of the glutamate and aspartate pools in brain are in close contact with intermediates of a fast-turning tricarboxylic acid cycle. 2. (14)C from [1-(14)C]acetate and [2-(14)C]acetate is incorporated to a much larger extent into glutamine than into glutamate. An examination of the time-course of (14)C incorporated into glutamine and glutamate reveals that glutamine is not formed from the glutamate pool, labelled extensively by glucose, but from a small glutamate pool. This small glutamate pool is not derived from an intermediate of a fast-turning tricarboxylic acid cycle. 3. It is proposed that two different tricarboxylic acid cycles exist in brain.