Degradation of 2-Carboxyarabinitol 1-Phosphate by a Specific Chloroplast Phosphatase

Holbrook, Gabriel P.; Bowes, George; Salvucci, Michael E.

doi:10.1104/pp.90.2.673

Cited by 48 publications

(32 citation statements)

References 18 publications

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“…This implies an interaction between CA 1-P metabolism and reactions on the reducing side of PSI. Additionally, in preliminary studies, it has been noted that CA 1-Pase activity is stimulated in vitro by several chloroplast metabolites, including NADPH, RuBP, and FBP (7,20). With P. vulgaris, appreciable levels of CA 1-P accumulation occur within 60 s under low-light conditions, but in other species the increase in inhibitor concentration may require more than 1 h (6, 10).…”

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confidence: 99%

“…To date, relatively little is known about the metabolism of CA 1-P, despite the fact that in many species it occupies more than half the Rubisco active sites in darkness (25). A plausible sequence of events allowing the light-dependent reversal of Rubisco inhibition would involve release of CA 1-P from the enzyme facilitated by Rubisco activase (15), followed by its phosphohydrolytic degradation catalyzed by CA l-Pase (4,7,21). The net reaction is dependent upon chloroplast electron transport, because treatment with DCMU inhibits reversal of Rubisco inhibition during reillumination (24).…”

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Regulation of 2-Carboxyarabinitol 1-Phosphatase

Holbrook¹,

Galasinski²,

Salvucci³

1991

Plant Physiol.

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The regulation of 2-carboxyarabinitol 1-phosphatase (CA 1-Pase) by phosphorylated effectors was studied with enzyme purified from tobacco (Nicotiana tabacum) leaves. CA 1-Pase activity was most stimulated by fructose 1,6-bisphosphate, exhibiting an Ao.5 value of 1.9 millimolar and a 10-fold enhancement of catalysis. With nbulose-1,5-bisphosphate, the AO.5 was 0.6 millimolar, and maximal stimulation of activity was 5.3-fold. Among the monophosphates, 3-phosphoglycerate and phosphoglycolate were more potent positive effectors than glyceraldehyde 3-phosphate, glucose 1-phosphate, glucose 6-phosphate, and dihydroxyacetone phosphate. Stimulation of CA 1-Pase by ribulose-1,5-bisphosphate and fructose 1,6-bisphosphate increased Vmax but did not appreciably alter Km (2-carboxyarabinitol 1-phosphate) values. Inorganic phosphate appeared to inhibit CA 1-Pase noncompetitively with respect to 2-carboxyarabinitol 1-phosphate, exhibiting a K, of 0.3 millimolar. The results suggest that these positive and negative effectors bind to a regulatory site on CA 1-Pase and may have a physiological role in the light regulation of this enzyme. Related experiments with CA 1-Pase inactivated by dialysis in the absence of dithiothreitol show that partial reactivation can be achieved in the presence of a range of reducing reagents, including dithiothreitol, cysteine, and reduced glutathione. This could imply an ancillary involvement of sulfhydryl reduction during light activation of CA 1-Pase in vivo. The enzyme was thermally stable up to 350C, in contrast to ribulose-1,5-bisphosphate carboxylase/oxygenase activase which lost activity above 300C. The activation energy for CA 1-Pase was calculated to be 56.14 kilojoules per mole.

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Regulation of 2-Carboxyarabinitol 1-Phosphatase

Holbrook¹,

Galasinski²,

Salvucci³

1991

Plant Physiol.

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“…Because the job was in the Tobacco and Forage Research Unit, and tobacco contained CA1P, he began investigating the relative contributions of activase and CA1P to the regulation of Rubisco in tobacco. These studies led to a collaboration with George Bowes and Gabe Holbrook, then a postdoc with George, that culminated in the identification of CA1P phosphatase, a specific phosphatase that metabolizes CA1P in light (Holbrook et al 1989). Back in Urbana, Simon Robinson joined Archie Portis on a sabbatical from Australia and was proceeding through a detailed characterization of activase, including elucidation of its ATPase activity (Robinson and Portis 1989).…”

Section: Ca1p -A Red Herring?mentioning

confidence: 99%

The discovery of Rubisco activase — yet another story of serendipity

Portis¹,

Salvucci²

2005

Discoveries in Photosynthesis

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A brief history of Rubisco (ribulose bisphosphate carboxylase oxygenase) research and the events leading to the discovery and initial characterization of Rubisco activase are described. Key to the discovery was the chance isolation of a novel Arabidopsis photosynthesis mutant. The characteristics of the mutant suggested that activation of Rubisco was not a spontaneous process in vivo, but involved a heritable factor. The search for the putative factor by 2D electrophoresis identified two polypeptides, genetically linked to Rubisco activation, that were missing in chloroplasts from the mutant. An assay for the activity of these polypeptides, which were given the name Rubisco activase, was developed after realizing the importance of including ribulose bisphosphate (RuBP) in the assay. The requirement for ATP and the subsequent identification of activase as an ATPase came about fortuitously, the result of a RuBP preparation that was contaminated with adenine nucleotides. Finally, the ability of activase to relieve inhibition of the endogenous Rubisco inhibitor, 2-carboxyarabinitol 1-phosphate, provided an early indication of the mechanism by which activase regulates Rubisco.Abbreviations: CA1P -2-carboxyarabinitol 1-phosphate; FBP -fructose bisphosphate; RuBP -ribulose bisphosphate; Rubisco -ribulose bisphosphate carboxylase oxygenase; Ru5P -ribulose 5-phosphate; SBP -sedoheptulose bisphosphate 'Much discussion, both inside and outside the lecture halls, centered upon the potentially important reports of endogenous compounds which inhibit or activate RuBPCO. The debate was fiercest over reports by M. Salvucci, A. Portis and co-workers of the presence in some tissues of a protein which is involved in the activation of RuBPCO. The suggestion that the protein is an enzyme, hence the name RuBPCO activase, appeared to raise some hackles.' J. A. M. Holtum and E. Latzko, 1987 Pre-activase history -a complex and schizophrenic RubiscoA brief look at some of the history of Rubisco research reveals a saga of surprises that will set an appropriate stage for describing the discovery of Rubisco activase. This most abundant plant protein masqueraded for many years as 'Fraction one' protein (Wildman and Bonner 1947;Kawashima and Wildman 1970) before its carboxylation activity was uncovered, beginning in 1954 (for historical accounts, see Weissbach and Horecker 1989; A.A. Benson, this issue; and S. Wildman, this issue). Many years later, its bifunctionality was revealed by discovery of its oxygenase activity (Bowes et al. 1971). The oxygenase

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“…Presumably in the plant, as photosynthesis slows in shade or dark conditions, this intermediate analog stabilizes the activated state of the enzyme. The absence of the 5-phosphate reduces the affinity of the analog by some four orders of magnitude compared with 2CABP, ensuring that it dissociates from the active site long enough to be degraded by a specific phosphatase (Gutteridge and Julien, 1989;Holbrook et al, 1989). Presumably, the process of release is assisted by interaction of the inhibited form of Rubisco with activase (Portis, 1990).…”

Section: Regulation Of Rubisco Actlvltymentioning

confidence: 99%