One of the major metabolic enzymes that have gained so much interest in scientists is 3-Mercaptopyruvate sulfurtransferase (3-MST). This enzyme occurs widely in nature (Bordo, 2002 and Jarabak, 1981).

It has been reported in several organisms ranging from humans to rats, fishes, and insects. It is a mitochondrial enzyme that has been concerned with the detoxification of cyanide, a potent toxin of the mitochondrial respiratory chain (Nelson et al., 2000). Among the several metabolic enzymes that carry out xenobiotic detoxification, 3-mercaptopyruvate sulfurtransferase is of utmost importance.

3-mercaptopyruvate sulfurtransferase functions in the detoxifications of cyanide; mediation of sulfur ion transfer to cyanide or to other thiol compounds. (Vandenet al., 1967).It is also required for the biosynthesis of thiosulfate. In combination with cysteine aminotransferase, it contributes to the catabolism of cysteine and it is important in generating hydrogen sulfide in the brain, retina and vascular endothelial cells (Shibuya et al., 2009). It also acquired different functions such as a redox regulation (maintenance of cellular redox homeostasis) and defense against oxidative stress, in the atmosphere under oxidizing conditionsNagaharaet al (2005).

Hydrogen sulfide (H2S) is an important synaptic modulator, signaling molecule, smooth muscle contractor and neuroprotectant (Hosokiet al., 1997). Its production by the 3-mercaptopyruvate sulfurtransferase and cysteine aminotransferase pathways is regulated by calcium ions (Hosokiet al., 1997).

Organisms that are exposed to cyanide poisoning usually have this enzyme in them. This could be in food as in the cyanogenicglucosides being consumed. It has been studied from a variety of sources, which include bacteria, yeasts, plants, and animals (Marcus Wischik, 1998).

Cyanide could be released into the bark of trees as a defense mechanism. There are an array of defensive compounds that make their parts (leaves, flowers, stems, roots, and fruits) distasteful or poisonous to predators. In response, however, the animals that feed on them have evolved over successive generations a range of measures to overcome these compounds and can eat the plant safely. The tree trunk offers a clear example of the variety of defenses available to plants (Marcus Wischik, 1998).

Oryctes rhinoceros larva is one of the organisms that are also exposed to cyanide toxicity because of the environment they are found.



3-Mercaptopyruvate sulfurtransferase (EC., is a member of the group, Sulfurtransferases (EC – 5), which are widely distributed enzymes of prokaryotes and eukaryotes (Bordoand Bork, 2002).

3-Mercaptopyruvate Sulfurtransferase is an enzyme that is part of the cysteine catabolic pathway. The enzyme catalyzes the conversion of 3-mercaptopyruvate to pyruvate and H2S (Shibuya et al., 2009). The deficiency of this enzyme will result in elevated urine concentrations of 3-mercaptopyruvate as well as 3-mercaptolactate, both in the form of disulfides with cysteine(Crawhallet al., 1969). It catalyzes the chemical reaction:

3-mercaptopyruvate + cyanide à  pyruvate + thiocyanate

3-mercaptopyruvate + thiolà   pyruvate + hydrogen sulphide (Sorbo 1957).

It transfers sulfur-containing groups and participates in cysteine metabolism (Shibuya et al., 2013). This enzyme catalyzes the transfer of sulfane sulfur from a donor molecule, such as thiosulfate or 3- mercaptopyruvate, to a nucleophile acceptor, such as cyanide or mercptoethanol.3-mercaptopyruvate is the known sulfur-donor substrate for 3-mercaptopyruvate sulfurtransferase (Porter & Baskin, 1995).

3-mercaptopyruvate sulfurtransferase is believed to function in the endogenous cyanide (CN) detoxification system because it is capable of transferring sulfur from 3-mercaptopyruvate (3-MP) to cyanide (CN), forming the less toxic thiocyanate (SCN) (Hylin and Wood, 1959). It is an important enzyme for the synthesis of hydrogen sulfide (H2S) in the brain (Shibuya et al., 2009).

The systematic name of this enzyme class is 3-mercaptopyruvate: cyanide sulfurtransferase. It is also called beta-mercaptopyruvatesulfurtransferase(Vachek and Wood, 1972)It is one of three known H2S producing enzymes in the body (Hylin and Wood, 1959). It is primarily localised in the mitochondria (Cipolloneet al., 2008).

The expression levels of 3-MST in the brain during the fetal and postnatal periods are higher than those in the adult brain (unpublished data) although the promoter region shows characteristics of a typical housekeeping gene (Nagaharaet al., 2004). The observation is supported by the finding that3-MST expression in the cerebellum is decreased during the adult period (Shibuya et al., 2013). On the other hand, its expression level in the lung decreases from the perinatal period. These facts suggest that 3-MST could function in the fetal and postnatal brain. It was reported that serotonin signaling via the 5-HT1A receptor in the brain during the early developmental stage plays a critical role in the establishment of innate anxiety during the early developmental stage (Richardson-Jones et al., 2011).

In the rat, 3-MST possesses 2 redox-sensing molecular switches (Nagahara and Katayama, 2005). A catalytic-site cysteine and an intersubunitdisulfide bond serve as a thioredoxin-specific molecular switch (Nagaharaet al., 2007). The intermolecular switch is not observed in prokaryotes and plants, which emerged into the atmosphere under reducing conditions (Nagahara, 2013). As a result, it acquired different functions such as a redox regulation (maintenance of cellular redox homeostasis) and defense against oxidative stress, in the atmosphere under oxidizing conditions (Nagaharaet al., 2005).

Moreover, 3-MST can produce H2S (or HS−) as a biofactor (Shibuya et al., 2009), which cystathionine β-synthase and cystathionine γ-lyase also can generate (Abe and Kimura, 1996). Interestingly 3-MST can uniquely produce SOx in the redox cycle of persulfide formed at the low-redox catalytic-site cysteine (Nagaharaet al., 2012). As an alternative hypothesis on the pathogenesis of the symptoms, H2S (or HS−) and/or SOxcould suppress anxiety-like behavior, and therefore, defects in these molecules could increase anxiety-like behavior. However, no microanalysis method has been established to quantify H2S (or HS−) and SOxat the physiological level (Ampolaet al., 1969).

MCDU was first recognized and reported in 1968 as an inherited metabolic disorder caused by congenital 3-MST insufficiency or deficiency. Most cases were associated with mental retardation (Ampolaet al, 1969) while the pathogenesis remains unknown.

Human MCDU was reported to be associated with behavioral abnormalities, mental retardation (Crawhall, 1985), hypokinetic behavior, and grand mal seizures and anomalies (flattened nasal bridge and excessively arched palate) (Ampolaet al, 1969); however, the pathogenesis has not been clarified since MCDU was recognized more than 40 years ago. Macroscopic anomalies were associated in 1 case (Ampolaet al, 1969); however, this could be an accidental combination. 3-MST deficiency also induced higher brain dysfunction in mice without macroscopic and microscopic abnormalities in the brain. 3-MST seems to play a critical role in the central nervous system, i.e., to establish normal anxiety (Richardson et al., 2011)


3-MST is widely distributed in prokaryotes and eukaryotes (Jarabak, 1981).  It is localized in the cytoplasm and mitochondria, but not all cells contain 3-MST (Nagaharaet al., 1998).


Human mercaptopyruvatesulfurtransferase (MPST; EC. belongs to the family of sulfurtransferases (Vandenet al., 1967). These enzymes catalyze the transfer of sulfur to a thiophilic acceptor (Sorbo 1957), where MPST has a preference for 3-mercapto sulfurtransferase as the sulfur-donor. MPST plays a central role in both cysteine degradation and cyanide detoxification. In addition, deficiency in MPST activity has been proposed to be responsible for a rare inheritable disease known as mercaptolactate-cysteine disulfiduria (MCDU) (Hannestadet al, 2006).


3-Mercaptopyruvate sulfurtransferasecatalyzes the reaction from mercaptopyruvate (SHCH2C (= O)COOH)) to pyruvate (CH3C(= O)COOH) in cysteine catabolism (Vackek and Wood, 1972). The enzyme is widely distributed in prokaryotes and eukaryotes (Jarabak, 1981).

This disulfide bond serves as a thioredoxin-specific molecular switch. On the other hand, a catalytic-site cysteine is easily oxidized to form a low-redox potential sulfenate which results in loss of activity (Nahagaraet al., 2005). Then, thioredoxin can uniquely restore the activity (Nagahara, 2013).

Thus, a catalytic site cysteine contributes to redox-dependent regulation of 3-MST activity serving as a redox-sensing molecular switch (Nahagara, 2013). These findings suggest that 3-MST serves as an antioxidant protein and partly maintain cellular redox homeostasis. Further, it was proposed that 3-MST can produce hydrogen sulfide (H2S) by using a persulfurated acceptor substrate (Shibuya et al, 2009).

As an alternative functional diversity of 3-MST, it has been recently demonstrated in-vitro that 3-MST can produce sulfur oxides (SOx) in the redox cycle of persulfide (S-S-) formed at the catalytic site of the reaction intermediate (Nagaharaet al, 2012).


The molecular formula of 3-MST is C3H4O3S (Vachek and Wood, 1972).

3-MST has a molecular weight of 120.127g/mol or 23800 Daltons (as summarized by PubChem compound).


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How To Write Chapter Three Of Your Research Project (Research Methodology)

  • Methodology In Research Paper

    Chapter three of the research project or the research methodology is another significant part of the research project writing. In developing the chapter three of the research project, you state the purpose of research, research method you wish to adopt, the instruments to be used, where you will collect your data, types of data collection, and how you collected it.

    This chapter explains the different methods to be used in the research project. Here you mention the procedures and strategies you will employ in the study such as research design, study design in research, research area (area of the study), the population of the study, etc. You also tell the reader your research design methods, why you chose a particular method, method of analysis, how you planned to analyze your data.

    Your methodology should be written in a simple language such that other researchers can follow the method and arrive at the same conclusion or findings.

    You can choose a survey design when you want to survey a particular location or behavior by administering instruments such as structured questionnaires, interviews, or experimental; if you intend manipulating some variables.

    The purpose of chapter three (research methodology) is to give an experienced investigator enough information to replicate the study. Some supervisors do not understand this and require students to write what is in effect, a textbook.

    A research design is used to structure the research and to show how all of the major parts of the research project, including the sample, measures, and methods of assignment, work together to address the central research questions in the study. The chapter three should begin with a paragraph reiterating the purpose of research. It is very important that before choosing design methods try and ask yourself the following questions: Will I generate enough information that will help me to solve the research problem by adopting this method?

    Method vs Methodology

    I think the most appropriate in methods versus methodology is to think in terms of their inter-connectedness and relationship between both. You should not beging thinking so much about research methods without thinking of developing a research methodology.

    Metodologia or methodology is the consideration of your research objectives and the most effective method and approach to meet those objectives. That is to say that methodology in research paper is the first step in planning a research project work.

    Design Methodology: Methodological Approach

    Example of methodology in research paper, you are attempting to identify the influence of personality on a road accident, you may wish to look at different personality types, you may also look at accident records from the FRSC, you may also wish to look at the personality of drivers that are accident victims, once you adopt this method, you are already doing a survey, and that becomes your metodologia or methodology.

    Your methodology should aim to provide you with the information to allow you to come to some conclusions about the personalities that are susceptible to a road accident or those personality types that are likely to have a road accident.

    The following subjects may or may not be in the order required by a particular institution of higher education, but all of the subjects constitute a defensible in metodologia or methodology chapter.

    Click here to complete this article - How To Write Chapter Three Of Your Research Project (Research Methodology)


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