Enzymes最新文献

Tyrosinases (TYR) play a key role in melanin biosynthesis by catalyzing two reactions: monophenolase and diphenolase activities. Despite low amino acid sequence homology, TYRs from various organisms (from bacteria to humans) have similar active site architectures and catalytic mechanisms. The active site of the TYRs contains two copper ions coordinated by histidine (His) residues. The catalytic mechanism of TYRs involves electron transfer between copper sites, leading to the hydroxylation of monophenolic compounds to diphenols and the subsequent oxidation of these to corresponding dopaquinones. Although extensive studies have been conducted on the structure, catalytic mechanism, and enzymatic capabilities of TYRs, some mechanistic aspects are still debated. This chapter will delve into the structure of the active site, catalytic function, and inhibition mechanism of TYRs. The goal is to improve our understanding of the molecular mechanisms underlying TYR activity. This knowledge can help in developing new strategies to modulate TYR function and potentially treat diseases linked to melanin dysregulation.

Bacterial tyrosinase is a copper-containing metalloenzyme with diverse physio-chemical properties, that have been identified in various bacterial strains, including actinobacteria and proteobacteria. Tyrosinases are responsible for the rate-limiting catalytic steps in melanin biosynthesis and enzymatic browning. The physiological role of bacterial tyrosinases in melanin biosynthesis has been harnessed for the production of coloring and dyeing agents. Additionally, bacterial tyrosinases have the capability of cross-linking activity, demonstrated material functionalization applications, and applications in food processing with varying substrate specificities and stability features. These characteristics make bacterial tyrosinases a valuable alternative to well-studied mushroom tyrosinases. The key feature of substrate specificity of bacterial tyrosinase has been exploited to engineer biosensors that have the ability to detect the minimal amount of different phenolic compounds. Today, the world is facing the challenge of multi-drugs resistance in various diseases, especially antibiotic resistance, skin cancer, enzymatic browning of fruits and vegetables, and melanogenesis. To address these challenges, medicinal scientists are developing novel chemotherapeutic agents by inhibiting bacterial tyrosinases. To serve this purpose, heterocyclic compounds are of particular interest due to their vast spectrum of biological activities and their potential as effective tyrosinase inhibitors. In this chapter, a plethora of research explores applications of bacterial tyrosinases in different fields, such as the production of dyes and pigments, catalytic applications in organic synthesis, bioremediation, food and feed applications, biosensors, wool fiber coating and the rationalized synthesis, and structure-activity relationship of bacterial tyrosinase inhibitors.

Computational studies have significantly advanced the understanding of tyrosinase (TYR) function, mechanism, and inhibition, accelerating the development of more effective and selective inhibitors. This chapter provides an overview of in silico studies on TYR inhibitors, emphasizing key inhibitory chemotypes and the main residues involved in ligand-target interactions. The chapter discusses tools applied in the context of TYR inhibitor development, e.g., structure-based virtual screening, molecular docking, artificial intelligence, and machine learning algorithms.

Bacterial carbonic anhydrases (BCAs, EC 4.2.1.1) are indispensable enzymes in microbial physiology because they facilitate the hydration of carbon dioxide (CO₂) to bicarbonate ions (HCO₃^-) and protons (H⁺), which are crucial for various metabolic processes and cellular homeostasis. Their involvement spans from metabolic pathways, such as photosynthesis, respiration, to organic compounds production, which are pivotal for bacterial growth and survival. This chapter elucidates the diversity of BCA genetic families, categorized into four distinct classes (α, β, γ, and ι), which may reflect bacterial adaptation to environmental niches and their metabolic demands. The diversity of BCAs is essential not only for understanding their physiological roles but also for exploring their potential in biotechnology. Knowledge of their diversity enables researchers to develop innovative biocatalysts for industrial applications, including carbon capture technologies to convert CO₂ emissions into valuable products. Additionally, BCAs are relevant to biomedical research and drug development because of their involvement in bacterial pathogenesis and microbial survival within the host. Understanding the diversity and function of BCAs can aid in designing targeted therapeutics that interfere with bacterial metabolism and potentially reduce the risk of infections.

Carbonic anhydrases (CAs) are ubiquitous enzymes that are found in all kingdoms of life. Though different classes of CAs vary in their roles and structures, their primary function is to catalyze the reaction between carbon dioxide and water to produce bicarbonate and a proton. Neisseria gonorrhoeae encodes for three distinct CAs (NgCAs) from three different families: an α-, a β-, and a γ-isoform. This chapter details the differences between the three NgCAs, summarizing their subcellular locations, roles, essentiality, structures, and enzyme kinetics. These bacterial enzymes have the potential to be drug targets; thus, previous studies have investigated the inhibition of NgCAs-primarily the α-isoform. Therefore, the classes of inhibitors that have been shown to bind to the NgCAs will be discussed as well. These classes include traditional CA inhibitors, such as sulfonamides, phenols, and coumarins, as well as non-traditional inhibitors including anions and thiocarbamates.

Tyrosinase, a pivotal enzyme in melanin biosynthesis, orchestrates the pigmentation process in humans, affecting skin, hair, and eye color. This chapter examines the three-dimensional structure and functional aspects of tyrosinases from various sources, highlighting their di-metal ion coordination crucial for catalytic activity. I explore the biochemical pathwayscheme catalyzed by tyrosinase, specifically the oxidation of L-tyrosine to L-dopaquinone, a precursor in melanin synthesis. Detailed structural analyses, including 3D structures obtained from X-ray crystallography and computational modeling, reveal key insights into the enzyme's active site, variations among tyrosinases, and substrate binding mechanisms. Furthermore, the chapter investigates the role of human tyrosinase variants, their inhibitors, essential for developing therapeutic and cosmetic applications targeting hyperpigmentation disorders. Structural characterizations of tyrosinase-inhibitor complexes provide a foundation for designing effective inhibitors, with compounds like kojic acid, L-mimosine, and (S)-3-amino-tyrosine demonstrating significant inhibitory potential. This comprehensive examination of the structure, function, and inhibition mechanisms of tyrosinase offers avenues for innovative treatments in biotechnology, health, and beyond.

Recent research has identified a novel class of carbonic anhydrases (CAs), designated ι-CA, predominantly found in marine diatoms, eukaryotic algae, cyanobacteria, bacteria, and archaea genomes. This class has garnered attention owing to its unique biochemical properties and evolutionary significance. Through bioinformatic analyses, LCIP63, a protein initially annotated with an unknown function, was identified as a potential ι-CA in the marine diatom Thalassiosira pseudonana. Subsequent biochemical characterization revealed that LCIP63 has CA activity and its preference for manganese ions over zinc, indicative of evolutionary adaptation to marine environments. Further exploration of bacterial ι-CAs, exemplified by Burkholderia territorii ι-CA (BteCAι), demonstrated catalytic efficiency and sensitivity to sulfonamide and inorganic anion inhibitors, the classical CA inhibitors (CAIs). The classification of ι-CAs into two variant types based on their sequences, distinguished by the COG4875 and COG4337 domains, marks a significant advancement in our understanding of these enzymes. Structural analyses of COG4337 ι-CAs from eukaryotic microalgae and cyanobacteria thereafter revealed a distinctive structural arrangement and a novel catalytic mechanism involving specific residues facilitating CO₂ hydration in the absence of metal ion cofactors, deviating from canonical CA behavior. These findings underscore the biochemical diversity within the ι-CA class and highlight its potential as a target for novel antimicrobial agents. Overall, the elucidation of ι-CA properties and mechanisms advances our knowledge of carbon metabolism in diverse organisms and underscores the complexity of CA evolution and function.

Tyrosinases (TYRs) are enzymes found in various organisms that are crucial for melanin biosynthesis, coloration, and UV protection. They play vital roles in insect cuticle sclerotization, mollusk shell formation, fungal and bacterial pigmentation, biofilm formation, and virulence. Structurally, TYRs feature copper-binding sites that are essential for catalytic activity, facilitating substrate oxidation via interactions with conserved histidine residues. TYRs exhibit diversity across animals, plants, fungi, mollusks, and bacteria, reflecting their roles and function. Eukaryotic TYRs undergo post-translational modifications, such as glycosylation, which affect protein folding and activity. Bacterial TYRs are categorized into five types based on their structural variation, domain organization and enzymatic properties, showing versatility across bacterial species. Moreover, bacterial TYRs, akin to fungal TYRs, have been implicated in the synthesis of secondary metabolites with antimicrobial properties. TYRs share significant sequence homology with hemocyanins, oxygen-carrier proteins in mollusks and arthropods, highlighting their evolutionary relationships. The evolution of TYRs underscores the dynamic nature of these enzymes and reflects adaptive strategies across diverse taxa.

Carbonic anhydrase metalloenzymes are encoded in genomes throughout all kingdoms of life with a conserved function catalyzing the reversible conversion of CO₂ to bicarbonate. Carbonic anhydrases have been well-investigated in humans, but are still relatively understudied in bacterial organisms, including Enterococci. Studies over the past decade have presented bacterial carbonic anhydrases as potential drug targets, with some chemical scaffolds potently inhibiting the Enterococcus carbonic anhydrases in vitro and displaying antimicrobial efficacy against Enterococcus organisms. While carbonic anhydrases in Enterococci still have much to be explored, hypotheses may be drawn from similar Gram-positive organisms for which known information exists about carbonic anhydrase function and relevance. Within this chapter is reported information and rational hypotheses regarding the subcellar locations, potential physiological roles, essentiality, structures, and kinetics of carbonic anhydrases in Enterococci.

Carbonic anhydrases belonging to the α-class are widely distributed in bacterial species. These enzymes have been isolated from bacteria with completely different characteristics including both Gram-negative and Gram-positive strains. α-CAs show a considerable similarity when comparing the biochemical, kinetic and structural features, with only small differences which reflect the diverse role these enzymes play in Nature. In this chapter, we provide a comprehensive overview on bacterial α-CA data, with a highlight to their potential biomedical and biotechnological applications.