Polyphosphate--an ancient energy source and active metabolic regulator

Area of Science:

• Biochemistry
• Molecular Biology
• Microbiology

Background:

• Polyphosphate (PP) is an energy-rich molecule synthesized and stored in microbial granules.
• It serves as an energy source and phosphate donor, vital for producing essential biomolecules and regulating gene expression.
• Polyphosphate kinases (PPKs) are key enzymes orchestrating PP metabolism and function.

Purpose of the Study:

• To review historical information, biochemical characteristics, and functional roles of polyphosphate kinases (PPKs).
• To explore the classification of PPKs based on function and homology.
• To discuss PPK roles in stress response, potential biotechnological applications, and an endosymbiotic origin hypothesis.

Main Methods:

• Literature review of existing research on polyphosphate and polyphosphate kinases.
• Comparative analysis of PPK classifications (functional and homology-based).
• Discussion of biochemical properties, stress response roles, and biotechnological potential.

Main Results:

• PPKs are categorized into three functional groups (PPK1, PPK2, PPK3) and three homology groups (EcPPK1, PaPPK2, ScVTC).
• PPs play critical roles in cellular energy metabolism, biosynthesis of vital molecules, and gene regulation.
• PPKs are implicated in cellular stress responses and present opportunities for biotechnology.

Conclusions:

• Polyphosphate kinases are essential enzymes with diverse roles in microbial physiology.
• Understanding PPK diversity and function is key to unlocking their biotechnological applications.
• A hypothesis suggests endosymbiotic origins for polyphosphate and calcium-rich organelles from ancient protocells.