Gütlich M, Witter K, Bourdais J, Veron M, Rödl W, Ziegler I. Control of 6-(D-threo-1',2'-dihydroxypropyl) pterin (dictyopterin) synthesis during aggregation of Dictyostelium discoideum. Involvement of the G-protein-linked signalling pathway in the regulation of GTP cyclohydrolase I activity.
Biochem J 1996;
314 ( Pt 1):95-101. [PMID:
8660315 PMCID:
PMC1217057 DOI:
10.1042/bj3140095]
[Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
6-(D-threo-1',2'-Dihydroxypropylpterin (dictyopterin) has been identified in extracts of growing Dictyostelium dicoideum cells [Klein, Thiery and Tatischeff (1990) Eur. J. Biochem. 187, 665-669]. We demonstrate that it originates from GTP by de novo biosynthesis and that the first committed step is catalysed by GTP cyclohydrolase I, yielding dihydroneopterin triphosphate [neopterin is 6-(D-erythro-1',2',3'-trihydroxypropyl) pterin]. The GTP cyclohydrolase I activity is found in the cytosolic fraction and in a membrane-associated form. The level of a 0.9 kb mRNA coding for GTP cyclohydrolase I decreases to about 10% of its initial value within 2 h after Dictyostelium cells start development induced by starvation. In the cytosolic fraction, the specific activities of GTP cyclohydrolase I, as well as the concentrations of (6R/S)-5,6,7,8-tetrahydrodictyopterin (H4dictyopterin), follow this decline of the mRNA level. In the particulate fraction, however, the specific activities of GTP cyclohydrolase I and, in consequence, H4dictyopterin synthesis, transiently increase and reach a maximum after 4-5 h of development. The time-course of H4dictyopterin concentrations in the starvation medium closely correlates with its production in the membrane fraction. The activity of membrane-associated GTP cyclohydrolase I can be increased by pre-incubation of the cell lysate with guanosine 5'-[gamma-thio]triphosphate and Mg2+. This GTP analogue does not serve as a substrate and has no direct effect on the enzyme activity, indicating that a G-protein-linked signalling pathway is involved in the regulation of GTP cyclohydrolase I activity and thus in H4dictyopterin production during early development of D. discoideum.
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