Polyphosphate Chain Length Determination in the Range of Two to Several Hundred P-Subunits with a New Enzyme Assay and 31P NMR

In-vivo functions and regulation of polyphosphate in the vascular system

PURPOSE OF REVIEW

Polyphosphate, an inorganic polymer consisting of linearly linked phosphate subunits, is ubiquitously found in living organisms. Functions and regulation of the polymer have been analyzed in plants, bacteria and yeast; however, the roles of polyphosphate in mammals are still emerging.

RECENT FINDINGS

In contrast to synthetic polyphosphate that has been extensively utilized in ex-vivo studies, natural polyphosphate is complexed with bivalent cations (mostly Ca 2+ ) and regardless of chain length, forms microparticles that are retained on the surface of procoagulant platelets, platelet-derived microparticles and cancer extracellular vesicles. On cell surfaces, these Ca 2+ /polyphosphate aggregates initiate the factor XII-driven contact system, triggering proinflammatory and procoagulant reactions through the kallikrein kinin system and intrinsic pathway of coagulation, respectively. Polyphosphate inhibitors interfere with thrombosis while sparing hemostasis, replicating the effect of factor XII neutralizing agents. Furthermore, polyphosphate binds to platelet factor 4, which has implications for autoimmune thrombotic diseases, such as heparin-induced thrombocytopenia (HIT) and vaccine-induced thrombotic thrombocytopenia (VITT), potentially contributing to their pathogenesis. The metabolism and organ-specific distribution of the polymer remain incompletely defined and is the topic of ongoing research.

SUMMARY

Polyphosphate acts as a procoagulant and proinflammatory mediator. Neutralizing polyphosphate provides well tolerated thromboprotection, mimicking the effects of factor XII deficiency.

Biotechnological production of polyphosphate from industrial wash water

Phosphate is mined from phosphate rock, which is a limited resource on a human time scale. For a sustainable phosphate supply, strategies for efficient use and recycling of phosphate must be developed. A German chemical company produces annually wash water containing phosphate and other inorganic substances (e.g., sodium, potassium, sulfate, and chloride) at a ton scale. Chemical precipitation is mostly used for phosphate removal. In this study, a biotechnological process utilizing Saccharomyces cerevisiae to upcycle phosphate-containing wastewater into pure sodium polyphosphate in powder form was developed. The process comprises fermentation and downstream processing (polyphosphate yields: 25% and 36%, respectively). The polyphosphate quality was independent of the wash water composition. Polyphosphate with a purity of 23% molar ratio Na to Na, K, and Mg of > 90%, and with an average chain length of 12.5 phosphate subunits was produced. The upcycled polyphosphate can be reused compared to phosphate fertilizer in many different applications. Overall, the here developed process can contribute to truly slowing down phosphate mining and finally enable a sustainable utilization of phosphate. Thereby, the benefit of the process is the cascade use of phosphate, reducing the need for phosphate rock before the phosphate ends up in the soil and ultimately in the sea.

Inorganic Polyphosphate, Mitochondria, and Neurodegeneration

With an aging population, the presence of aging-associated pathologies is expected to increase within the next decades. Regrettably, we still do not have any valid pharmacological or non-pharmacological tools to prevent, revert, or cure these pathologies. The absence of therapeutical approaches against aging-associated pathologies can be at least partially explained by the relatively lack of knowledge that we still have regarding the molecular mechanisms underlying them, as well as by the complexity of their etiopathology. In fact, a complex number of changes in the physiological function of the cell has been described in all these aging-associated pathologies, including neurodegenerative disorders. Based on multiple scientific manuscripts produced by us and others, it seems clear that mitochondria are dysfunctional in many of these aging-associated pathologies. For example, mitochondrial dysfunction is an early event in the etiopathology of all the main neurodegenerative disorders, and it could be a trigger of many of the other deleterious changes which are present at the cellular level in these pathologies. While mitochondria are complex organelles and their regulation is still not yet entirely understood, inorganic polyphosphate (polyP) could play a crucial role in the regulation of some mitochondrial processes, which are dysfunctional in neurodegeneration. PolyP is a well-preserved biopolymer; it has been identified in every organism that has been studied. It is constituted by a series of orthophosphates connected by highly energetic phosphoanhydride bonds, comparable to those found in ATP. The literature suggests that the role of polyP in maintaining mitochondrial physiology might be related, at least partially, to its effects as a key regulator of cellular bioenergetics. However, further research needs to be conducted to fully elucidate the molecular mechanisms underlying the effects of polyP in the regulation of mitochondrial physiology in aging-associated pathologies, including neurodegenerative disorders. With a significant lack of therapeutic options for the prevention and/or treatment of neurodegeneration, the search for new pharmacological tools against these conditions has been continuous in past decades, even though very few therapeutic approaches have shown potential in treating these pathologies. Therefore, increasing our knowledge about the molecular mechanisms underlying the effects of polyP in mitochondrial physiology as well as its metabolism could place this polymer as a promising and innovative pharmacological target not only in neurodegeneration, but also in a wide range of aging-associated pathologies and conditions where mitochondrial dysfunction has been described as a crucial component of its etiopathology, such as diabetes, musculoskeletal disorders, and cardiovascular disorders.

The Multiple Roles of Polyphosphate in Ralstonia eutropha and Other Bacteria

An astonishing variety of functions has been attributed to polyphosphate (polyP) in prokaryotes. Besides being a reservoir of phosphorus, functions in exopolysaccharide formation, motility, virulence and in surviving various forms of stresses such as exposure to heat, extreme pH, oxidative agents, high osmolarity, heavy metals and others have been ascribed to polyP. In this contribution, we will provide a historical overview on polyP, will then describe the key proteins of polyP synthesis, the polyP kinases, before we will critically assess of the underlying data on the multiple functions of polyP and provide evidence that - with the exception of a P-storage-function - most other functions of polyP are not relevant for survival of Ralstonia eutropha, a biotechnologically important beta-proteobacterial species.

Fixing the Broken Phosphorus Cycle: Wastewater Remediation by Microalgal Polyphosphates

Phosphorus (P), in the form of phosphate derived from either inorganic (Pi) or organic (Po) forms is an essential macronutrient for all life. P undergoes a biogeochemical cycle within the environment, but anthropogenic redistribution through inefficient agricultural practice and inadequate nutrient recovery at wastewater treatment works have resulted in a sustained transfer of P from rock deposits to land and aquatic environments. Our present and near future supply of P is primarily mined from rock P reserves in a limited number of geographical regions. To help ensure that this resource is adequate for humanity's food security, an energy-efficient means of recovering P from waste and recycling it for agriculture is required. This will also help to address excess discharge to water bodies and the resulting eutrophication. Microalgae possess the advantage of polymeric inorganic polyphosphate (PolyP) storage which can potentially operate simultaneously with remediation of waste nitrogen and phosphorus streams and flue gases (CO2, SOx, and NOx). Having high productivity in photoautotrophic, mixotrophic or heterotrophic growth modes, they can be harnessed in wastewater remediation strategies for biofuel production either directly (biodiesel) or in conjunction with anaerobic digestion (biogas) or dark fermentation (biohydrogen). Regulation of algal P uptake, storage, and mobilization is intertwined with the cellular status of other macronutrients (e.g., nitrogen and sulphur) in addition to the manufacture of other storage products (e.g., carbohydrate and lipids) or macromolecules (e.g., cell wall). A greater understanding of controlling factors in this complex interaction is required to facilitate and improve P control, recovery, and reuse from waste streams. The best understood algal genetic model is Chlamydomonas reinhardtii in terms of utility and shared resources. It also displays mixotrophic growth and advantageously, species of this genus are often found growing in wastewater treatment plants. In this review, we focus primarily on the molecular and genetic aspects of PolyP production or turnover and place this knowledge in the context of wastewater remediation and highlight developments and challenges in this field.

Biotechnological synthesis of water-soluble food-grade polyphosphate with Saccharomyces cerevisiae

Inorganic polyphosphate (polyP) is the polymer of phosphate. Water-soluble polyPs with average chain lengths of 2-40 P-subunits are widely used as food additives and are currently synthesized chemically. An environmentally friendly highly scalable process to biosynthesize water-soluble food-grade polyP in powder form (termed bio-polyP) is presented in this study. After incubation in a phosphate-free medium, generally regarded as safe wild-type baker's yeast (Saccharomyces cerevisiae) took up phosphate and intracellularly polymerized it into 26.5% polyP (as KPO₃ , in cell dry weight). The cells were lyzed by freeze-thawing and gentle heat treatment (10 min, 70°C). Protein and nucleic acid were removed from the soluble cell components by precipitation with 50 mM HCl. Two chain length fractions (42 and 11P-subunits average polyP chain length, purity on a par with chemically produced polyP) were obtained by fractional polyP precipitation (Fraction 1 was precipitated with 100 mM NaCl and 0.15 vol ethanol, and Fraction 2 with 1 final vol ethanol), drying, and milling. The physicochemical properties of bio-polyP were analyzed with an enzyme assay, ³¹ P nuclear magnetic resonance spectroscopy, and polyacrylamide gel electrophoresis, among others. An envisaged application of the process is phosphate recycling from waste streams into high-value bio-polyP.

Methods for the Analysis of Polyphosphate in the Life Sciences

Inorganic polyphosphate (polyP) is the polymer of orthophosphate and can be found in all living organisms. For polyP characterization, one or more of six parameters are of interest: the molecular structure (linear, cyclic, or branched), the concentration, the average chain length, the chain length distribution, the cellular localization, and the cation composition. Here, the merits, limitations, and critical parameters of the state-of-the-art methods for the analysis of the six parameters from the life sciences are discussed. With this contribution, we aim to lower the entry barrier into the analytics of polyP, a molecule with prominent, yet often incompletely understood, contributions to cellular function.