1887

Abstract

Summary: Phosphoribulokinase (ATP:-ribulose-5-phosphate 1-phosphotransferase, EC 2.7.1.19) was purified from the cyanobacterium . The enzyme had a molecular weight of 230000, as determined by gel filtration, and a pH optimum of 8·6. Divalent cations were essential for activity, maximal activity being supported by Mg, while Mn, Ca and Co were less effective. AMP, ADP, phosphoenolpyruvate, aspartate and malate inhibited enzyme activity completely at 1 m. No effects on phosphoribulokinase activity were observed with NAD, NADH, NADP or NADPH at up to 10 mm or with glyoxylate at up to 20 m. The enzyme was activated in semi-purified extracts by the addition of dithiothreitol and reduced glutathione. SDS-PAGE of SDS-dissociated enzyme revealed only one polypeptide band of molecular weight 40000. This suggests that phosphoribulokinase is a hexamer consisting of six subunits of identical size.

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/content/journal/micro/10.1099/00221287-130-4-999
1984-04-01
2020-11-24
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http://instance.metastore.ingenta.com/content/journal/micro/10.1099/00221287-130-4-999
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