Fructose 1,6-Bisphosphatase Form B from Synechococcus leopoliensis Hydrolyzes both Fructose and Sedoheptulose Bisphosphate

Abstract

ABSTRACITThe substrate specificity of purified fructose bisphosphatase form B from Synechococcus leopoliensis (EC 3.1.3.11; cf. K-P Gerbling, M Steup, E Latzko 1985 Eur J Biochem 147: 207-215) has been investigated. Of the phosphate esters tested only fructose 1,6-bisphosphate and sedoheptulose 1,7-bisphosphate were hydrolyzed by the enzyme. Both sugar bisphosphates were cleaved at the carbon 1-ester. Fructose-and sedoheptulose bisphosphate stabilized the activated (i.e. tetrameric) state of the enzyme and prevented a slow inactivation that is observed in the absence of sugar bisphosphates. With the activated enzyme, kinetic constants (half-saturating substrate concentrations, maximal reaction velocity, and the catalytical constant) were similar for both fructose-and sedoheptulose bisphosphate. The data suggest that fructose bisphosphatase form B from Synechococcus leopoliensis can catalyze both bisphosphatase reactions within the reductive pentose phosphate cycle.In the reductive pentose phosphate cycle two sugar bisphosphate esters, FBP' and sedoheptulose 1,7-bisphosphate, are cleaved specifically at the carbon 1-ester. Both phosphatase reactions probably play an important role in regulating the flux through the entire cycle (12, 17; but see 7). However, conflicting data have been reported on the enzymology of both phosphatase activities. In some photo-and chemoautotrophic cells, fructose and sedoheptulose bisphosphatase activities have been attributed to distinct enzymes specific either for sedoheptulose bisphosphate or FBP (13,20). In contrast, in other organisms fructose bisphosphatase has been shown to hydrolyze sedoheptulose bisphosphate as well (1,2,18) and the existence of a sedoheptulose bisphosphate specific phosphatase has been questioned (1 1).

Higher-plant chloroplast and cytosolic fructose-1,6-bisphophosphatase isoenzymes: origins via duplication rather than prokaryote-eukaryote divergence

“…However, the bisphosphatase reactions subsequent to these two aldolase reactions in higherplant chloroplasts are catalysed by distinct, separate and specific FBP [47] and SBP enzymes [10]. In eubacteria by contrast, single 'FBP' enzymes are known which possess dual substrate specificity for both sedoheptulose-1,7-bisphosphate and fructose-1,6-bisphosphate [1,2,18,43]. This dual specificity has also been demonstrated for the cloned enzymes from Rhodobacter [19] and Alcaligenes [46], which possess sufficient activity with either substrate to catalyze both reactions in the Calvin cycle.…”

“…Accordingly, these are designated as fructose-l,6/sedoheptulose-1,7-bisphosphatases (FBP/SBP). Some proteo-and cyanobacteria have been suggested to possess two [ 18] or even three [46] enzymes with FBP activity. Some non-photosynthetic eubacteria, such as E. coli, possess FBP which lacks SBP activity [17].…”

Origin and Distribution of Calvin Cycle Fructose and Sedoheptulose Bisphosphatases in Plantae and Complex Algae: A Single Secondary Origin of Complex Red Plastids and Subsequent Propagation via Tertiary Endosymbioses

“…Chloroplast SBPase and FBPase of land plants have replaced the bispecific enzyme of cyanobacteria that either uses sedoheptulose-1,7-bisphosphate or fructose-1,6-bisphosphate as a substrate (Gerbling et al 1986). Thus, SBP may represent a promising test system for open questions of eukaryotic evolution including the examination of the relationships of complex algae that originated via eukaryote-toeukaryote endosymbioses (see above).…”

Characterization of Fructose 1,6-Bisphosphatase and Sedoheptulose 1,7-Bisphosphatase from the Facultative Ribulose Monophosphate Cycle Methylotroph Bacillus methanolicus

“…In the Calvin cycle, both SBPase and FBPase operate. While in photosynthetic bacteria, such as cyanobacteria, a single promiscuous enzyme carries out both reactions (36), in green plants, two separate enzymes catalyze the individual reactions. SBPases are homodimeric, comprising two identical subunits of 35 to 38 kDa, and are immunologically distinct from FBPase (37,38).…”