Pramod Kumar Yadav

Bio: Pramod Kumar Yadav is an academic researcher from University of Michigan. The author has contributed to research in topics: Cystathionine beta synthase & Pectin lyase. The author has an hindex of 19, co-authored 36 publications receiving 1645 citations. Previous affiliations of Pramod Kumar Yadav include Deen Dayal Upadhyay Gorakhpur University.

Pectin lyase: A review

Abstract: Pectin lyase acts on the pectic substances that occur as structural polysaccharides in the middle lamella and primary cell walls of higher plants. This enzyme has potential applications in food, paper and textile industries. Since new applications of this enzyme are emerging there is a scientific need to explore the important aspects of the enzyme specifically the catalytic efficiency and possible sources. Though the research work on pectin lyase has been done for the last six decades but there is no exclusive review on pectin lyase so far available in the literature. This review tries to fill this gap by providing all relevant information exclusively for pectin lyase. The topics covered in this review are a brief description of the substrate pectin, enzymes related to pectin lyase, assay procedures, sources, purification and characterization, structural aspects, substrate specificity, molecular biology, biotechnological applications and future prospects of pectin lyases.

Organization of the human mitochondrial hydrogen sulfide oxidation pathway.

Abstract: Sulfide oxidation is expected to play an important role in cellular switching between low steady-state intracellular hydrogen sulfide levels and the higher concentrations where the physiological effects are elicited. Yet despite its significance, fundamental questions regarding how the sulfide oxidation pathway is wired remain unanswered, and competing proposals exist that diverge at the very first step catalyzed by sulfide quinone oxidoreductase (SQR). We demonstrate that, in addition to sulfite, glutathione functions as a persulfide acceptor for human SQR and that rhodanese preferentially synthesizes rather than utilizes thiosulfate. The kinetic behavior of these enzymes provides compelling evidence for the flow of sulfide via SQR to glutathione persulfide, which is then partitioned to thiosulfate or sulfite. Kinetic simulations at physiologically relevant metabolite concentrations provide additional support for the organizational logic of the sulfide oxidation pathway in which glutathione persulfide is the first intermediate formed.

Biosynthesis and Reactivity of Cysteine Persulfides in Signaling

Abstract: Hydrogen sulfide (H2S) elicits pleiotropic physiological effects ranging from modulation of cardiovascular to CNS functions. A dominant method for transmission of sulfide-based signals is via posttranslational modification of reactive cysteine thiols to persulfides. However, the source of the persulfide donor and whether its relationship to H2S is as a product or precursor is controversial. The transsulfuration pathway enzymes can synthesize cysteine persulfide (Cys–SSH) from cystine and H2S from cysteine and/or homocysteine. Recently, Cys–SSH was proposed as the primary product of the transsulfuration pathway with H2S representing a decomposition product of Cys–SSH. Our detailed kinetic analyses demonstrate a robust capacity for Cys–SSH production by the human transsulfuration pathway enzymes, cystathionine beta-synthase and γ-cystathionase (CSE) and for homocysteine persulfide synthesis from homocystine by CSE only. However, in the reducing cytoplasmic milieu where the concentration of reduced thiols is...

Structure and Kinetic Analysis of H2S Production by Human Mercaptopyruvate Sulfurtransferase.

Abstract: Mercaptopyruvate sulfurtransferase (MST) is a source of endogenous H2S, a gaseous signaling molecule implicated in a wide range of physiological processes. The contribution of MST versus the other two H2S generators, cystathionine β-synthase and γ-cystathionase, has been difficult to evaluate because many studies on MST have been conducted at high pH and have used varied reaction conditions. In this study, we have expressed, purified, and crystallized human MST in the presence of the substrate 3-mercaptopyruvate (3-MP). The kinetics of H2S production by MST from 3-MP was studied at pH 7.4 in the presence of various physiological persulfide acceptors: cysteine, dihydrolipoic acid, glutathione, homocysteine, and thioredoxin, and in the presence of cyanide. The crystal structure of MST reveals a mixture of the product complex containing pyruvate and an active site cysteine persulfide (Cys248-SSH) and a nonproductive intermediate in which 3-MP is covalently linked via a disulfide bond to an active site cysteine. The crystal structure analysis allows us to propose a detailed mechanism for MST in which an Asp-His-Ser catalytic triad is positioned to activate the nucleophilic cysteine residue and participate in general acid-base chemistry, whereas our kinetic analysis indicates that thioredoxin is likely to be the major physiological persulfide acceptor for MST. Background: Mercaptopyruvate sulfurtransferase (MST) generates H2S, a signaling molecule. Results: The detailed kinetics and crystal structure of human MST with bound substrate are reported. Conclusion: Thioredoxin is the preferred persulfide acceptor from MST. Significance: The structure provides molecular insights into activation and stabilization of MST reaction intermediates.

Improved tag-switch method reveals that thioredoxin acts as depersulfidase and controls the intracellular levels of protein persulfidation

Abstract: Hydrogen sulfide (H2S) has emerged as a signalling molecule capable of regulating several important physiological functions such as blood pressure, neurotransmission and inflammation. The mechanisms behind these effects are still largely elusive and oxidative posttranslational modification of cysteine residues (protein persulfidation or S-sulfhydration) has been proposed as the main pathway for H2S-induced biological and pharmacological effects. As a signalling mechanism, persulfidation has to be controlled. Using an improved tag-switch assay for persulfide detection we show here that protein persulfide levels are controlled by the thioredoxin system. Recombinant thioredoxin showed an almost 10-fold higher reactivity towards cysteine persulfide than towards cystine and readily cleaved protein persulfides as well. This reaction resulted in H2S release suggesting that thioredoxin could be an important regulator of H2S levels from persulfide pools. Inhibition of the thioredoxin system caused an increase in intracellular persulfides, highlighting thioredoxin as a major protein depersulfidase that controls H2S signalling. Finally, using plasma from HIV-1 patients that have higher circulatory levels of thioredoxin, we could prove depersulfidase role in vivo.

Industrial use of immobilized enzymes

Abstract: Although many methods for enzyme immobilization have been described in patents and publications, relatively few processes employing immobilized enzymes have been successfully commercialized. The cost of most industrial enzymes is often only a minor component in overall process economics, and in these instances, the additional costs associated with enzyme immobilization are often not justified. More commonly the benefit realized from enzyme immobilization relates to the process advantages that an immobilized catalyst offers, for example, enabling continuous production, improved stability and the absence of the biocatalyst in the product stream. The development and attributes of several established and emerging industrial applications for immobilized enzymes, including high-fructose corn syrup production, pectin hydrolysis, debittering of fruit juices, interesterification of food fats and oils, biodiesel production, and carbon dioxide capture are reviewed herein, highlighting factors that define the advantages of enzyme immobilization.

Microbial enzymes: industrial progress in 21st century

Abstract: Biocatalytic potential of microorganisms have been employed for centuries to produce bread, wine, vinegar and other common products without understanding the biochemical basis of their ingredients. Microbial enzymes have gained interest for their widespread uses in industries and medicine owing to their stability, catalytic activity, and ease of production and optimization than plant and animal enzymes. The use of enzymes in various industries (e.g., food, agriculture, chemicals, and pharmaceuticals) is increasing rapidly due to reduced processing time, low energy input, cost effectiveness, nontoxic and eco-friendly characteristics. Microbial enzymes are capable of degrading toxic chemical compounds of industrial and domestic wastes (phenolic compounds, nitriles, amines etc.) either via degradation or conversion. Here in this review, we highlight and discuss current technical and scientific involvement of microorganisms in enzyme production and their present status in worldwide enzyme market.

Chemical Biology of H2S Signaling through Persulfidation.

Abstract: Signaling by H2S is proposed to occur via persulfidation, a posttranslational modification of cysteine residues (RSH) to persulfides (RSSH). Persulfidation provides a framework for understanding the physiological and pharmacological effects of H2S. Due to the inherent instability of persulfides, their chemistry is understudied. In this review, we discuss the biologically relevant chemistry of H2S and the enzymatic routes for its production and oxidation. We cover the chemical biology of persulfides and the chemical probes for detecting them. We conclude by discussing the roles ascribed to protein persulfidation in cell signaling pathways.

A Unifying Mechanism for Mitochondrial Superoxide Production during Ischemia-Reperfusion Injury.

Abstract: Ischemia-reperfusion (IR) injury occurs when blood supply to an organ is disrupted—ischemia—and then restored—reperfusion—leading to a burst of reactive oxygen species (ROS) from mitochondria. It has been tacitly assumed that ROS production during IR is a non-specific consequence of oxygen interacting with dysfunctional mitochondria upon reperfusion. Recently, this view has changed, suggesting that ROS production during IR occurs by a defined mechanism. Here we survey the metabolic factors underlying IR injury and propose a unifying mechanism for its causes that makes sense of the huge amount of disparate data in this area and provides testable hypotheses and new directions for therapies.

Edible films from pectin: Physical-mechanical and antimicrobial properties - A review

Abstract: Pectin is one of the main components of the plant cell wall chemically constituted by poly α1–4-galacturonic acids. According to its degree of esterification with methanol, pectin can be classified as high methoxyl pectin or low methoxyl pectin. In food industry, pectin is listed as generally recognized as safe (GRAS) by the Food and Drug Administration and is used as gelling, stabilizing, or thickening agent in food products such as jams, yoghurt drinks, fruity milk drinks, and ice cream. Due to its biodegradability, biocompatibility, edibility, and versatile chemical and physical properties (such as gelation, selective gas permeability, etc), pectin is a suitable polymeric matrix for the elaboration of edible films intended as active food packaging. Active packaging is a packaging system which possesses attributes beyond basic barrier properties that are achieved by adding active ingredients in the packaging material and/or using functionally active polymers. When the packaging system has antimicrobial activity, the packaging limits or prevents the microbial growth by extending the lag period and reducing the growth rate of microorganisms. This review describes the main methods for elaborating pectin edible films, principal characterization techniques for determining their physical-mechanical properties, and applications of pectin edible films as antimicrobial food packaging. Finally, legislation and future trends regarding the use of pectin edible films are also discussed.