A novel class of conserved sucrose-phosphate phosphatases highlights the diversity of cyanobacterial sucrose metabolism

Cyanobacteria, a group of photosynthetic organisms, are known for their diverse sucrose metabolism. In plants, algae, and cyanobacteria, sucrose is typically synthesized through a process involving sucrose-phosphate synthase, followed by its dephosphorylation into sucrose by sucrose-phosphate phosphatase (SPP). However, within cyanobacterial genomes, multiple homologs of SPP proteins, known as SPP-like proteins, have been identified.

Some of these SPP-like proteins lack crucial residues necessary for sucrose 6-phosphate binding. A study focusing on the SPP-like protein encoded by the cyanobacterial model, Synechococcus elongatus PCC 7942, reveals that this protein exhibits biochemical activity similar to SPP, including dephosphorylating sucrose 6-phosphate. Additionally, it may possess physiological relevance in phosphatase activity on 3-phosphoglycerate (3-PGA), a compound crucial for various metabolic pathways.

The bioinformatic analysis of these proteins suggests that they are highly conserved across different cyanobacterial species and form distinct phylogenetic clades. These findings highlight the broader distribution of SPP-like proteins compared to the more commonly studied SPP proteins. This research suggests that the SPP-like family of proteins represents a well-conserved group of phosphatases within cyanobacteria, potentially evolving a broader substrate specificity than their SPP counterparts.

The implications of these findings extend to the regulation of sucrose biosynthesis and other key steps in cyanobacterial central carbon metabolism.