Effect of intramitochondrial Mg2+ on citrulline synthesis in rat liver mitochondria.
A correlation was found between mitochondrial matrix free magnesium ([Mg2+]m), measured by means of the fluorescent indicator Mag-Fura-2, and citrulline synthesis in rat liver mitochondria. The variation of [Mg2+]m from 0.05 to 1.7 mM by changes in external Mg2+, induced a 20 +/- 8.5% increase in the rate of citrulline synthesis, whereas a further increase of [Mg2+]m to 3.3 mM induced a return to basal values. The increase in [Mg2+]m, as well as the diminution of external pH, also promoted an elevation of matrix free Ca2+ ([Ca2+]m). An increase in [Ca2+]m, at constant [Mg2+]m and pH, resulted in a 3-fold stimulation of citrulline synthesis. The data suggest that [Mg2+]m may modulate the rate of citrulline synthesis through a direct interaction with carbamoyl-phosphate synthase I (ammonia) and, indirectly, by changing the levels of matrix Ca2+.
Rodríguez-Zavala
J S
JS
Instituto de Investigaciones Químico-Biológicas, Universidad Michoacana de San Nicolás de Hidalgo, México.
Saavedra-Molina
A
A
Moreno-Sánchez
R
R
D000818:Animals; D002118:Calcium / Q000378:metabolism; D002956:Citrulline / Q000096:biosynthesis*; D005456:Fluorescent Dyes; D016257:Fura-2 / Q000031:analogs & derivatives; D008274:Magnesium / Q000032:analysis / Q000502:physiology*; D008930:Mitochondria, Liver / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar
D005456:Fluorescent Dyes; C058776:2-(2-(5-carboxy)oxazole)-5-hydroxy-6-aminobenzofuran-N,N,O-triacetic acid; D002956:Citrulline; D008274:Magnesium; D002118:Calcium; D016257:Fura-2