NDLI: Two strictly polyphosphate-dependent gluco(manno)kinases from diazotrophic Cyanobacteria with potential to phosphorylate hexoses from polyphosphates

Content Provider	Springer Nature Link
Author	Albi, Tomás Serra, Aurelio
Copyright Year	2014
Abstract	The single-copy genes encoding putative polyphosphate–glucose phosphotransferases (PPGK, EC 2.7.1.63) from two nitrogen-fixing Cyanobacteria, Nostoc sp. PCC7120 and Nostoc punctiforme PCC73102, were cloned and functionally characterized. In contrast to their actinobacterial counterparts, the cyanobacterial PPGKs have shown the ability to phosphorylate glucose using strictly inorganic polyphosphates (polyP) as phosphoryl donors. This has proven to be an economically attractive reagent in contrast to the more costly ATP. Cyanobacterial PPGKs had a higher affinity for medium–long-sized polyP (greater than ten phosphoryl residues). Thus, longer polyP resulted in higher catalytic efficiency. Also in contrast to most their homologs in Actinobacteria, both cyanobacterial PPGKs exhibited a modest but significant polyP-mannokinase activity as well. Specific activities were in the range of 180–230 and 2–3 μmol min−1 mg−1 with glucose and mannose as substrates, respectively. No polyP-fructokinase activity was detected. Cyanobacterial PPGKs required a divalent metal cofactor and exhibited alkaline pH optima (approx. 9.0) and a remarkable thermostability (optimum temperature, 45 °C). The preference for Mg2+ was noted with an affinity constant of 1.3 mM. Both recombinant PPGKs are homodimers with a subunit molecular mass of ca. 27 kDa. Based on database searches and experimental data from Southern blots and activity assays, closely related PPGK homologs appear to be widespread among unicellular and filamentous mostly nitrogen-fixing Cyanobacteria. Overall, these findings indicate that polyP may be metabolized in these photosynthetic prokaryotes to yield glucose (or mannose) 6-phosphate. They also provide evidence for a novel group-specific subfamily of strictly polyP-dependent gluco(manno)kinases with ancestral features and high biotechnological potential, capable of efficiently using polyP as an alternative and cheap source of energy-rich phosphate instead of costly ATP. Finally, these results could shed new light on the evolutionary origin of sugar kinases.
Starting Page	3887
Ending Page	3900
Page Count	14
File Format	PDF
ISSN	01757598
Journal	Applied Microbiology and Biotechnology
Volume Number	99
Issue Number	9
e-ISSN	14320614
Language	English
Publisher	Springer Berlin Heidelberg
Publisher Date	2014-11-09
Publisher Place	Berlin, Heidelberg
Access Restriction	Subscribed
Subject Keyword	Gluco(manno)kinase Hexokinase Cyanobacteria PolyP-dependent Polyphosphate Regeneration of ATP Microbiology Microbial Genetics and Genomics Biotechnology
Content Type	Text
Resource Type	Article
Subject	Medicine Applied Microbiology and Biotechnology Biotechnology

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