Hyaluronan synthases; mechanisms, myths, & mysteries of three types of unique bifunctional glycosyltransferases

Advances and principles of hyaluronic acid production, extraction, purification, and its applications: A review

Hyaluronic acid (HA) is a linear, unbranched polysaccharide composed of repeating disaccharide units of N-acetyl-d-glucosamine and D-glucuronic acid. It plays a crucial role in promoting soft tissue growth, elasticity, and scar reduction. The growing demand for HA in pharmaceutical and cosmetic applications has provoked extensive research into diverse production strategies. Current efforts focus on bacterial and yeast fermentation. However, the extraction process presents a significant challenge due to the complex nature of source materials like fermentation broth, which contains numerous components and solutes. Achieving high extraction yields and purity requires careful consideration of extraction techniques. This study provides a comprehensive overview of the primary methodologies employed for HA production, elaborating on the advantages and disadvantages of each approach. Additionally, it highlights recent advancements in HA extraction and purification, with a particular emphasis on bacterial sources and the applications of HA. This review critically evaluates current HA production strategies, identifies key challenges hindering scalability and efficiency, and discusses innovative solutions under development to overcome these limitations.

Expression and molecular characterization of an intriguing hyaluronan synthase (HAS) from the symbiont "Candidatus Mycoplasma liparidae" in snailfish

Background

Hyaluronan synthases (HASs) are ubiquitous in living organisms, and the hyaluronic acid (HA) synthesized by them are important to their body and well used in medicine, cosmetics and other fields. HAS from deep-sea creatures has not yet been explored before. The study aims to analyse the characteristics and enzyme kinetics of a novel hyaluronan synthase derived from the symbiont "Candidatus Mycoplasma liparidae" found in deep-sea snailfish (snHAS).

Methodology

snHAS was over-expressed using His 6 as tag in the study. The sequence alignment was conducted by Cluster W and then the phylogenetic analyse of HASs was performed by Mega 6.0 to investigate the position of snHAS during evolution. K m and V max were detected to study the enzyme kinetics of snHAS wildtype and its mutant. The molecular weight of HA was evaluated by high performance gel permeation chromatography (HPGPC). The cardiolipin was added to investigate whether it had a promoting effect on the snHAS.

Results

The length of snHAS was 933 bp with an open reading frame (ORF) of 310 amino acids. Unlike other repoted HASs, snHAS had no transmembrane region and was not classified into the currently known Class I or Class II. snHAS could synthesize hyaluronan with lower molecular weights using the substrates of uridine-diphosphate-N-acetylglucosamine (UDP-GlcNAc) and uridine-diphosphate-glucuronic acid (UDP-GlcA) in vitro. The K m values of snHAS were 258 ± 45 µM and 39 ± 5 µM for UDP-GlcNAc and UDP-GlcA, respectively, much lower than those from mice (K m for UDP-GlcA: 55 ± 5 µM; K m for UDP-GlcNAc: 870 ± 60 µM). The k cat/K m values of snHAS were 163.5 s-1 mM-1 and 8.08 s-1 mM-1 for UDP-GlcA and UDP-GlcNAc, respectively. Furthermore, the activity of snHAS was independent of cardiolipin.

Conclusions

snHAS was a novel HAS based on the characteristics of the animo acid sequence, which could produce low molecular weight of HA with high efficiency. This provides a molecular basis for the biosynthesis of low molecular weight of HA.

Regulating cellular metabolism and morphology to achieve high-yield synthesis of hyaluronan with controllable molecular weights

High-yield biosynthesis of hyaluronan (HA) with controllable molecular weights (MWs) remains challenging due to the poorly understood function of Class I HA synthase (HAS) and the metabolic imbalance between HA biosynthesis and cellular growth. Here, we systematically characterize HAS to identify crucial regions involved in HA polymerization, secretion, and MW control. We construct HAS mutants that achieve complete HA secretion and expand the MW range from 300 to 1400 kDa. By dynamically regulating UDP-glucose 6-dehydrogenase activity and applying an adaptive evolution approach, we recover cell normal growth with increased metabolic capacities. Final titers and productivities for high MW HA (500 kDa) and low MW HA (10 kDa) reach 45 g L-1 and 105 g L-1, 0.94 g L-1 h-1 and 1.46 g L-1 h-1, respectively. Our findings advance our understanding of HAS function and the interplay between cell metabolism and morphology, and provide a shape-guided engineering strategy to optimize microbial cell factories.

Microbes, macrophages, and melanin: a unifying theory of disease as exemplified by cancer

It is widely accepted that cancer mostly arises from random spontaneous mutations triggered by environmental factors. Our theory challenges the idea of the random somatic mutation theory (SMT). The SMT does not fit well with Charles Darwin's theory of evolution in that the same relatively few mutations would occur so frequently and that these mutations would lead to death rather than survival of the fittest. However, it would fit well under the theory of evolution, if we were to look at it from the vantage point of pathogens and their supporting microbial communities colonizing humans and mutating host cells for their own benefit, as it does give them an evolutionary advantage and they are capable of selecting genes to mutate and of inserting their own DNA or RNA into hosts. In this article, we provide evidence that tumors are actually complex microbial communities composed of various microorganisms living within biofilms encapsulated by a hard matrix; that these microorganisms are what cause the genetic mutations seen in cancer and control angiogenesis; that these pathogens spread by hiding in tumor cells and M2 or M2-like macrophages and other phagocytic immune cells and traveling inside them to distant sites camouflaged by platelets, which they also reprogram, and prepare the distant site for metastasis; that risk factors for cancer are sources of energy that pathogens are able to utilize; and that, in accordance with our previous unifying theory of disease, pathogens utilize melanin for energy for building and sustaining tumors and metastasis. We propose a paradigm shift in our understanding of what cancer is, and, thereby, a different trajectory for avenues of treatment and prevention.

Impacts of Hyaluronan on Extracellular Vesicle Production and Signaling

Hyaluronan (HA) is a critical component of cell and tissue matrices and an important signaling molecule. The enzymes that synthesize and process HA, as well as the HA receptors through which the signaling properties of HA are transmitted, have been identified in extracellular vesicles and implicated in context-specific processes associated with health and disease. The goal of this review is to present a comprehensive summary of the research on HA and its related receptors and enzymes in extracellular vesicle biogenesis and the cellular responses to vesicles bearing these extracellular matrix modulators. When present in extracellular vesicles, HA is assumed to be on the outside of the vesicle and is sometimes found associated with CD44 or the HAS enzyme itself. Hyaluronidases may be inside the vesicles or present on the vesicle surface via a transmembrane domain or GPI linkage. The implication of presenting these signals in extracellular vesicles is that there is a greater range of systemic distribution and more complex delivery media than previously thought for secreted HA or hyaluronidase alone. Understanding the context for these HA signals offers new diagnostic and therapeutic insight.

Structural insights into translocation and tailored synthesis of hyaluronan

Hyaluronan (HA) is an essential component of the vertebrate extracellular matrix. It is a heteropolysaccharide of N-acetylglucosamine (GlcNAc) and glucuronic acid (GlcA) reaching several megadaltons in healthy tissues. HA is synthesized and translocated in a coupled reaction by HA synthase (HAS). Here, structural snapshots of HAS provide insights into HA biosynthesis, from substrate recognition to HA elongation and translocation. We monitor the extension of a GlcNAc primer with GlcA, reveal the coordination of the uridine diphosphate product by a conserved gating loop and capture the opening of a translocation channel to coordinate a translocating HA polymer. Furthermore, we identify channel-lining residues that modulate HA product lengths. Integrating structural and biochemical analyses suggests an avenue for polysaccharide engineering based on finely tuned enzymatic activity and HA coordination.

How to Fabricate Hyaluronic Acid for Ocular Drug Delivery

This review aims to examine existing research on the development of ocular drug delivery devices utilizing hyaluronic acid (HA). Renowned for its exceptional biocompatibility, viscoelastic properties, and ability to enhance drug bioavailability, HA is a naturally occurring biopolymer. The review discussed specific mechanisms by which HA enhances drug delivery, including prolonging drug residence time on ocular surfaces, facilitating controlled drug release, and improving drug penetration through ocular tissues. By focusing on these unique functionalities, this review highlights the potential of HA-based systems to revolutionize ocular treatment. Various fabrication techniques for HA-based ocular drug delivery systems, including hydrogels, nanoparticles, and microneedles, are discussed, highlighting their respective advantages and limitations. Additionally, this review explores the clinical applications of HA-based devices in treating a range of ocular diseases, such as dry eye syndrome, glaucoma, retinal disorders, and ocular infections. By comparing the efficacy and safety profiles of these devices with traditional ocular drug delivery methods, this review aims to provide a comprehensive understanding of the potential benefits and challenges associated with HA-based systems. Moreover, this review discusses current limitations and future directions in the field, such as the need for standardized fabrication protocols, long-term biocompatibility studies, and large-scale clinical trials. The insights and advancements presented in this review aim to guide future research and development efforts, ultimately enhancing the effectiveness of ocular drug delivery and improving patient outcomes.

Anionic cardiolipin stabilizes the transmembrane region of hyaluronan synthase and promotes catalysis-relevant dynamics

Hyaluronic acid (HA) is a glycosaminoglycan essential for cellular processes and finding increasingly applications in medicine, pharmaceuticals, and cosmetics. While membrane-integrated Class I hyaluronan synthase (HAS) catalyzes HA synthesis in most organisms, the molecular mechanisms by which HAS-lipid interactions impact HAS catalysis remain unclear. This study employed coarse-grained molecular dynamics simulation combined with dimensionality reduction to uncover the interplay between lipids and Streptococcus equisimilis HAS (SeHAS). A minimum of 67 % cardiolipin is necessary for HA synthesis, as determined through simulations using gradient-composed membranes. The anionic cardiolipin stabilizes the cationic transmembrane regions of SeHAS and thereby maintains its conformation. Moreover, the highly dynamic cardiolipin is required to modulate the catalysis-relevant motions in HAS and thus facilitate HA synthesis. These findings provide molecular insights essential not only for understanding the physiological functions of HAS, but also for the development of cell factories and enzyme catalysts for HA production.

Chemoenzymatic synthesis with the Pasteurella hyaluronan synthase; production of a multitude of defined authentic, derivatized, and analog polymers

Hyaluronan (HA; [-3-GlcNAc-1-beta-4-GlcA-1-beta] n ), an essential matrix polysaccharide of vertebrates and the molecular camouflage coating in certain pathogens, is polymerized by "HA synthase" (HAS) enzymes. Three HAS classes have been identified with biotechnological utility, but only the Class II PmHAS from Pasteurella multocida Type A has been useful for preparation of very defined HA polymers in vitro. Two general chemoenzymatic strategies with different size products are possible: (1) repetitive step-wise extension reactions by sequential addition of a single monosaccharide from a donor UDP-sugar onto an acceptor (or "primer") comprised of a short glycosaminoglycan chain (e.g., HA di-, tri- or tetrasaccharide) or an artificial glucuronide yielding homogeneous oligosaccharides in the range of 2 to ~20 monosaccharide units (n = 1 to ~10), or (2) "one-pot" polymerization reactions employing acceptor-mediated synchronization with stoichiometric size control yielding quasi-monodisperse (i.e., polydispersity approaching 1; very narrow size distributions) polysaccharides in the range of ~7 kDa to ~2 MDa (n = ~17 to 5000). In either strategy, acceptors containing non-carbohydrate functionalities (e.g., biotin, fluorophores, amines) can add useful moieties to the reducing termini of HA chains at 100% efficiency. As a further structural diversification, PmHAS can utilize a variety of unnatural UDP-sugar analogs thus adding novel groups (e.g., trifluoroacetyl, alkyne, azide, sulfhydryl) along the HA backbone and/or at its nonreducing terminus. This review discusses the current understanding and recent advances in HA chemoenzymatic synthesis methods using PmHAS. This powerful toolbox has potential for creation of a multitude of HA-based probes, therapeutics, drug conjugates, coatings, and biomaterials.

Utility of Authentic 13C-Labeled Disaccharide to Calibrate Hyaluronan Content Measurements by LC-MS

Hyaluronan (hyaluronic acid, HA), a key glycosaminoglycan in the extracellular matrix, plays crucial roles in various physiological and pathological processes, including development, tissue hydration, inflammation, and tumor progression. Traditional methods for HA quantification, such as ELISA-like assays, often have limitations in sensitivity and specificity, particularly for lower molecular weight HA. In this work, we introduce a coupled liquid chromatographic-tandem mass spectrometric (LC-MS/MS) method that employs a chemoenzymatically synthesized 13C-labeled lyase-derived authentic HA disaccharide calibrant for quantification of HA at the nanogram level. The method was validated against three HA polysaccharides with the sizes of ~33, 210, and 540 kDa. We applied this quantification technique to mouse tissues and plasma from both healthy and acetaminophen-induced acute liver injury mice. Our data revealed a ~75-fold increase in HA concentration in the liver of acetaminophen-injured mice with a concomitant depletion from plasma. Overall, our method offers a robust, universal, and highly sensitive tool for HA analysis in diverse biological samples that will advance the investigation of the roles of this polysaccharide in human disease conditions.

Hyaluronic Acid in Nanopharmaceuticals: An Overview

Hyaluronic acid (HA) is a naturally occurring, long, unbranched polysaccharide that plays a critical role in maintaining skin structure and hydration. Its unique properties make it a valuable component in the field of nanopharmaceuticals. The combination of HA into nanopharmaceuticals enhances its ability to interact with various therapeutic agents, improving the delivery and efficacy of drugs. HA-based nanoparticles, including solid lipid nanoparticles, and polymeric nanogels, offer controlled release, enhanced stability, and targeted delivery of therapeutic agents. These innovations significantly improve therapeutic outcomes and reduce side effects, making HA an essential tool in modern medicine. In general, HA-modified liposomes enhance drug encapsulation and targeting, while HA-modified solid lipid nanoparticles (SLNs) provide a solid lipid core for drug encapsulation, offering controlled release and stability. This article provides an overview of the potential applications and recent advancements of HA in nanopharmaceuticals, emphasizing its significant impact on the evolving field of targeted drug delivery and advanced therapeutic strategies. By delving into the unique properties of HA and its compatibility with various therapeutic agents, this review underscores the promising potential of HA in revolutionizing nanopharmaceuticals.

Nitrilotriacetic Acid Functionalized Microgels for Efficient Immobilization of Hyaluronan Synthase

Enzymes play a vital role in synthesizing complex biological molecules like hyaluronic acid (HA). Immobilizing enzymes on support materials is essential for their efficient use and reuse in multiple cycles. Microgels, composed of cross-linked, highly swollen polymer networks, are ideal for enzyme uptake owing to their high porosity. This study demonstrates the immobilization of His6-tagged hyaluronan synthase from Pasteurella multocida (PmHAS) onto nitrilotriacetic acid functionalized microgels using different bivalent ions (Ni2+, Co2+, Mn2+, Mg2+, and Fe2+) via metal affinity binding. The results indicate that using Ni2+ yields the microgels with the highest enzyme uptake and HA formation. The immobilized PmHAS enables repetitive enzymatic production, producing high molecular weight HAs with decreasing dispersities in each step. Furthermore, the highest reported yield of HA with high molecular weight for immobilized PmHAS is achieved. This system establishes a foundation for continuous HA formation, with future works potentially enhancing PmHAS stability through protein engineering.

A biological guide to glycosaminoglycans: current perspectives and pending questions

Mammalian glycosaminoglycans (GAGs), except hyaluronan (HA), are sulfated polysaccharides that are covalently attached to core proteins to form proteoglycans (PGs). This article summarizes key biological findings for the most widespread GAGs, namely HA, chondroitin sulfate/dermatan sulfate (CS/DS), keratan sulfate (KS), and heparan sulfate (HS). It focuses on the major processes that remain to be deciphered to get a comprehensive view of the mechanisms mediating GAG biological functions. They include the regulation of GAG biosynthesis and postsynthetic modifications in heparin (HP) and HS, the composition, heterogeneity, and function of the tetrasaccharide linkage region and its role in disease, the functional characterization of the new PGs recently identified by glycoproteomics, the selectivity of interactions mediated by GAG chains, the display of GAG chains and PGs at the cell surface and their impact on the availability and activity of soluble ligands, and on their move through the glycocalyx layer to reach their receptors, the human GAG profile in health and disease, the roles of GAGs and particular PGs (syndecans, decorin, and biglycan) involved in cancer, inflammation, and fibrosis, the possible use of GAGs and PGs as disease biomarkers, and the design of inhibitors targeting GAG biosynthetic enzymes and GAG-protein interactions to develop novel therapeutic approaches.

The spatial separation of basic amino acids is similar in RHAMM and hyaluronan binding peptide P15-1 despite different sequences and conformations

Peptides that increase pro-reparative responses to injury and disease by modulating the functional organization of hyaluronan (HA) with its cell surface binding proteins (e.g., soluble receptor for hyaluronan-mediated motility [RHAMM] and integral membrane CD44) have potential therapeutic value. The binding of RHAMM to HA is an attractive target, since RHAMM is normally absent or expressed at low levels in homeostatic conditions, but its expression is significantly elevated in the extracellular matrix during tissue stress, response-to-injury, and in cancers and inflammation-based diseases. The HA-binding site in RHAMM contains two closely spaced sequences of clustered basic amino acids, in an alpha-helical conformation. In the present communication, we test whether an alpha-helical conformation is required for effective peptide binding to HA, and competitive disruption of HA-RHAMM interaction. The HA-binding RHAMM-competitive peptide P15-1, identified using the unbiased approach of phage display, was examined using circular dichroism spectroscopy and the conformation-predictive AI-based AlphaFold2 algorithm. Unlike the HA-binding site in RHAMM, peptide P15-1 was found to adopt irregular conformations in solution rather than alpha helices. Instead, our structural analysis suggests that the primary determinant of peptide-HA binding is associated with a specific clustering and spacing pattern of basic amino acids, allowing favorable electrostatic interaction with carboxylate groups on HA.

Advances in hyaluronic acid production: Biosynthesis and genetic engineering strategies based on Streptococcus - A review

Hyaluronic acid (HA), which is a highly versatile glycosaminoglycan, is widely applied across the fields of food, cosmetics, and pharmaceuticals. It is primary produced through Streptococcus fermentation, but the product presents inherent challenges concerning consistency and potential pathogenicity. However, recent strides in molecular biology have paved the way for genetic engineering, which facilitates the creation of high-yield, nonpathogenic strains adept at synthesizing HA with specific molecular weights. This comprehensive review extensively explores the molecular biology underpinning pivotal HA synthase genes, which elucidates the intricate mechanisms governing HA synthesis. Moreover, it delineates various strategies employed in engineering HA-producing strains.