Understanding the changes affecting the plant cell wall is a key element in addressing its functional role in plant growth and in the response to stress. Pectins, which are the main constituents of the primary cell wall in dicot species, play a central role in the control of cellular adhesion and thereby of the rheological properties of the wall. This is likely to be a major determinant of plant growth. How the discrete changes in pectin structure are mediated is thus a key issue in our understanding of plant development and plant responses to changes in the environment. In particular, understanding the remodelling of homogalacturonan (HG), the most abundant pectic polymer, by specific enzymes is a current challenge in addressing its fundamental role. HG, a polymer that can be methylesterified or acetylated, can be modified by HGMEs (HG-modifying enzymes) which all belong to large multigenic families in all species sequenced to date. In particular, both the degrees of substitution (methylesterification and/or acetylation) and polymerization can be controlled by specific enzymes such as pectin methylesterases (PMEs), pectin acetylesterases (PAEs), polygalacturonases (PGs), or pectate lyases-like (PLLs). Major advances in the biochemical and functional characterization of these enzymes have been made over the last 10 years. This review aims to provide a comprehensive, up to date summary of the recent data concerning the structure, regulation, and function of these fascinating enzymes in plant development and in response to biotic stresses.

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Homogalacturonan-modifying enzymes: structure, expression, and roles in plants

Pectinases are the growing enzymes of biotechnological sector, showing gradual increase in their market. They hold a leading position among the commercially produced industrial enzymes. These enzymes are ecofriendly tool of nature that are being used extensively in various industries like wine industry; food industry; paper industry for bleaching of pulp and waste paper recycling; in the processing of fruit–vegetables, tea–coffee, animal feed; extraction of vegetable oil and scouring of plant fibres. Moreover, enzymatic catalysis is preferred over other chemical methods, since it is more specific, less aggressive and saves energy. This is the review which covers the information available on the applicability potential of this group of enzymes in various sectors.

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Microbial pectinases: an ecofriendly tool of nature for industries

Phytate, phenolic compounds and fiber are known anti-nutritional factors (ANFs) that contribute to the low bioaccessibility and bioavailability of iron and zinc in plant foods. Better insight into the localization of minerals and anti-nutritional factors in plant tissues, as well as on the mechanisms of interaction between minerals and ANFs, may lead to better targeted processing for improvement of the bioaccessibility of minerals in plant foods. This review highlights the subcellular distribution of iron and zinc and their ANFs in plant organs, as well as the mechanisms of interaction between these metals and their ANFs. These insights are then used to better clarify the role of various processing technologies, like mechanical treatments, soaking, germination, fermentation and heating, on improving the bioaccessibility of iron and zinc in plant foods.

Role of processing on bioaccessibility of minerals: Influence of localization of minerals and anti-nutritional factors in the plant

Exploration of extremophiles for high temperature biotechnological processes.

People have exploited the biocatalytic potential of microorganisms for centuries to produce wine, vinegar, bread, and so forth without understanding their biochemical basis. Microbial enzymes are also used as biocatalysts in various industrial processes in an economical and environmentally-friendly way, as compared with chemical catalysis. Over the past few decades, the use of microbial enzymes in bioprocesses has increased rapidly, because of their catalytic activity, as well as stability. Worldwide, enzymes produced from microorganisms have been extensively investigated for isolation, purification, characterization, and applications. Microbial enzymes have diverse applications in the food, pharmaceutical, and biotechnological industries, and so forth. Commercially, many recombinant enzymes from bacteria and fungi are used in various bioprocesses. Modern techniques such as metagenomics and genomics can be used to discover new microbial enzymes, whose catalytic properties can be improved further using molecular techniques. Moreover, the screening of novel enzymes that are capable of catalyzing new reactions is constantly required. The discovery of new enzymes will provide clues for the design of new enzymatic processes. This chapter provides an overview of industrially important microbial enzymes; particularly their sources and applications.

Microbial Enzymes—An Overview

Today pectinases are upcoming industrially important bacterial enzymes. It can be produced by a variety of microorganisms. These enzymes act on pectin, which is the major component of middle lamella in plant cell wall. Pectinolytic enzymes are classified according to their mode of attack on the galacturonan part of the pectin molecules such as protopectinases, esterase’s and depolymerases. As we know that microbial enzymes work depends up on the type of enzymes application, temperature, concentration, and pH and so on, therefore, pectinase enzyme also differentiated according to their physical and chemical factors too. The biochemical structures of pectinases include members of all the major classes and the structure–function relationship, studies of a few available complexes of pectinases with substrate/analogs could be considered as prototypes for related family member and the molecular characterization of pectinolytic enzymes is also well documented. Furthermore, it provides a bird’s eye view of the possible application of these enzymes in commercial sector.

Microbial pectinase: sources, characterization and applications

Most pathogenic bacteria require iron for growth. However, this metal is not freely available in the mammalian host. Due to its poor solubility and propensity to catalyze the generation of reactive oxygen species, host iron is kept in solution bound to specialized iron binding proteins. Access to iron is an important factor in the outcome of bacterial infections; iron limitation frequently induces virulence and drives pathogenic interactions with host cells. Here, we review the response of Mycobacterium tuberculosis to changes in iron availability, the relevance of this response to TB pathogenesis, and its potential for the design of new therapeutic interventions.

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The Iron Response of Mycobacterium tuberculosis and Its Implications for Tuberculosis Pathogenesis and Novel Therapeutics

Mycobacterium tuberculosis (Mtb) secretes extracellular vesicles (EVs) containing a variety of proteins, lipoproteins, and lipoglycans. While emerging evidence suggests that EVs contribute to tuberculosis pathogenesis, the factors and molecular mechanisms involved in mycobacterial EV production have not been identified. In this study, we use a genetic approach to identify Mtb proteins that mediate vesicle release in response to iron limitation and antibiotic exposure. We uncover a critical role for the isoniazid‐induced, dynamin‐like proteins, IniA and IniC, in mycobacterial EV biogenesis. Further characterization of a Mtb iniA mutant shows that the production of EVs enables intracellular Mtb to export bacterial components into the extracellular environment to communicate with host cells and potentially modulate the immune response. The findings advance our understanding of the biogenesis and functions of mycobacterial EVs and provide an avenue for targeting vesicle production in vivo.

https://onlinelibrary.wiley.com/doi/pdfdirect/10.15252/embr.202255593

Nevadita Sharma

Papers

Microbial pectinase: sources, characterization and applications

The Iron Response of Mycobacterium tuberculosis and Its Implications for Tuberculosis Pathogenesis and Novel Therapeutics

Dynamin‐like proteins mediate extracellular vesicle secretion in Mycobacterium tuberculosis