Intrachloroplastidic mevalonate-activating enzymes in plant cells

doi:10.1016/0304-4211(73)90061-8

Plant Science Letters

Volume 1, Issue 9, September 1973, Pages 367-373

https://doi.org/10.1016/0304-4211(73)90061-8 Get rights and content

Abstract

Mevalonate phosphorylation by chloroplasts from Spinacia oleracea leaves, Agave americana leaves and Pinus pinaster seedlings is reported. Different modifications in the technique of chloroplast isolation by using an aqueous method have been introduced in order to protect the mevalonate kinase and phosphomevalonate kinase activities. The acid pH values of the preparations obtained by conventional methods from Agave americana and Pinus pinaster decrease their kinase activities; therefore, 0.35 M TrisHCl buffer, pH 7.9, containing 0.35 M mercaptoethanol must be used as the isolation medium. Ultrasonic treatment has been found to be the best method for chloroplast disruption in Spinacia oleracea and Agave americana, but a considerable inactivation of mevalonate kinase from Pinus pinaster has been observed after this treatment. The time course of mevalonic acid (MVA) phosphorylation by intrachloroplastidic enzymes was studied. Preparations from etiolated leaves of Agave americana also phosphorylated MVA, but their plastids are more fragile than those from green leaves.

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Properties and partial purification of mevalonate kinase from Agave americana
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Mevalonate kinase activity was demonstrated in acetone powder extracts from Agave americana leaves, flowers and scape. ATP was the most effective phosphate donor. The enzyme had an optimum pH of 7.9 in Tris-HCl buffer. Dialysis decreased the ability to phosphorylate mevalonic acid (MVA). Partially purified mevalonate kinase reached maximum activity in the presence of 2 mM Mn²⁺ or 6–8 mM Mg²⁺. Higher concentrations of Mn²⁺ were inhibitory, whereas higher concentrations of Mg²⁺ produced only a small decrease in the activity. The amount of mevalonate-5-phosphate (MVAP) formed depended on protein concentration and incubation time. During short incubations, the MVAP formed increased as protein concentration rose, whereas during prolonged incubations (1–6 hr), there was a decrease in the MVAP formed when a certain amount of protein was exceeded. It is suggested that MVAP formed was hydrolysed by a phosphatase present in the extracts. This interfering activity was eliminated when mevalonate kinase is partially purified. The apparent K_m values of the enzyme from leaves were 0.05 mM for MVA and 0. 14 mM for ATP. Similar K_m values are obtained with partially purified mevalonate kinase. The enzyme was purified by ammonium sulphate precipitation, Sephadex G-100 filtration and DEAE-Sephadex A-50 fractionation.
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Plant Science Letters

Intrachloroplastidic mevalonate-activating enzymes in plant cells

Abstract

J. Biol. Chem.

J. Biol. Chem.

Biochim. Biophys. Acta

Insect Biochem.

FEBS Letters

Phytochem.

Biochim. Biophys. Acta

Biochem. Biophys. Res. Commun.

Control of Isoprenoid Biosynthesis in Higher Plants

Properties and partial purification of mevalonate kinase from Agave americana

Mevalonate kinase from Pinus pinaster seedlings

Formation of isopentenyl diphosphate via mevalonate does not occur within etioplasts and etiochloroplasts of mustard (Sinapis alba L.) seedlings

MEVALONATE‐ACTIVATING ENZYMES IN WHEAT ETIOPLASTS