Molecular Modeling of Myrosinase from Brassica oleracea: A Structural Investigation of Sinigrin Interaction

Molecular Pathways Related to Sulforaphane as Adjuvant Treatment: A Nanomedicine Perspective in Breast Cancer

Because cancer is a multifactorial disease, it is difficult to identify the specific agents responsible for the disease's progression and development, but lifestyle and diet have been shown to play a significant role. Diverse natural compounds are demonstrating efficacy in the development of novel cancer therapies, including sulforaphane (1-isothiocyanate-4-(methylsulfinyl)butane), a compound found in broccoli and other cruciferous vegetables that promotes key biological processes such as apoptosis, cell cycle arrest, autophagy, and suppression of key signalling pathways such as the PI3K/AKT/mTOR pathway in breast cancer cells. However, one of the primary challenges with sulforaphane treatment is its low solubility in water and oral bioavailability. As a consequence, several investigations were conducted using this component complexed in nanoparticles, which resulted in superior outcomes when combined with chemotherapy drugs. In this study, we discuss the properties and benefits of sulforaphane in cancer therapy, as well as its ability to form complexes with nanomolecules and chemotherapeutic agents that synergize the antitumour response in breast cancer cells.

Broccoli Myrosinase cDNA Expression in Escherichia coli and Saccharomyces cerevisiae

Myrosinases (EC 3.2.1.147) are enzymes known for the generation of hydrolysis products that have a potential beneficial effect on human health. Their reaction mechanisms are widely studied, in order to improve and optimize secondary metabolite production processes. In this work, kinetic and biochemical properties of the broccoli myrosinase enzyme produced from its cDNA cloned in Escherichia coli and Saccharomyces cerevisiae were investigated. The results revealed that the thermal stability of the enzyme produced in S. cerevisiae was slightly higher (30 to 60 °C) than that of myrosinase produced in E. coli (20 to 50 °C). The effect of pH on the enzymatic activity was similar in both enzymes, with pH 3 being the optimum value under the reaction conditions used. The kinetic behavior of both enzymes was adjusted to the Michaelis–Menten model. The catalytic efficiency was up to 4 times higher in myrosinase produced in S. cerevisiae, compared to myrosinase produced in E. coli. The glycosylations present in the enzyme would be related to the formation of a dimeric quaternary structure and would not play an essential role in enzymatic activity, since both enzymes were biologically active. These results will probably allow the development of strategies for the production of bioactive metabolites of medical interest.

Improved Production of Recombinant Myrosinase in Pichia pastoris

The effect of the deletion of a 57 bp native signal sequence, which transports the nascent protein through the endoplasmic reticulum membrane in plants, on improved AtTGG1 plant myrosinase production in Pichia pastoris was studied. Myrosinase was extracellularly produced in a 3-liter laboratory fermenter using α-mating factor as the secretion signal. After the deletion of the native signal sequence, both the specific productivity (164.8 U/L/h) and volumetric activity (27 U/mL) increased more than 40-fold compared to the expression of myrosinase containing its native signal sequence in combination with α-mating factor. The deletion of the native signal sequence resulted in slight changes in myrosinase properties: the optimum pH shifted from 6.5 to 7.0 and the maximal activating concentration of ascorbic acid increased from 1 mM to 1.5 mM. Kinetic parameters toward sinigrin were determined: 0.249 mM (K_m) and 435.7 U/mg (V_max). These results could be applied to the expression of other plant enzymes.

Myrosinase: insights on structural, catalytic, regulatory, and environmental interactions

Glucosinolate-myrosinase is a substrate-enzyme defense mechanism present in Brassica crops. This binary system provides the plant with an efficient system against herbivores and pathogens. For humans, it is well known for its anti-carcinogenic, anti-inflammatory, immunomodulatory, anti-bacterial, cardio-protective, and central nervous system protective activities. Glucosinolate and myrosinase are spatially present in different cells that upon tissue disruption come together and result in the formation of a variety of hydrolysis products with diverse physicochemical and biological properties. The myrosinase-catalyzed reaction starts with cleavage of the thioglucosidic linkage resulting in release of a D-glucose and an unstable thiohydroximate-O-sulfate. The outcome of this thiohydroximate-O-sulfate has been shown to depend on the structure of the glucosinolate side chain, the presence of supplementary proteins known as specifier proteins and/or on the physiochemical condition. Myrosinase was first reported in mustard seed during 1939 as a protein responsible for release of essential oil. Until this date, myrosinases have been characterized from more than 20 species of Brassica, cabbage aphid, and many bacteria residing in the human intestine. All the plant myrosinases are reported to be activated by ascorbic acid while aphid and bacterial myrosinases are found to be either neutral or inhibited. Myrosinase catalyzes hydrolysis of the S-glycosyl bond, O-β glycosyl bond, and O-glycosyl bond. This review summarizes information on myrosinase, an essential component of this binary system, including its structural and molecular properties, mechanism of action, and its regulation and will be beneficial for the research going on the understanding and betterment of the glucosinolate-myrosinase system from an ecological and nutraceutical perspective.

Microbiota: a mediator to transform glucosinolate precursors in cruciferous vegetables to the active isothiocyanates

Isothiocyanates (ITCs), such as sulforaphane (SFN), exhibit powerful biological functions in fighting cancers, and cardiovascular and neurodegenerative diseases. They normally exist as glucosinolates (GLSs) in cruciferous vegetables, which are not themselves bioactive until they are degraded by myrosinase to form ITCs. Myrosinase coexists in the same plants but is normally kept apart from GLSs in different apparatus. A key point is that myrosinase is temperature sensitive and can be inactivated upon exposure to temperatures over 60 °, as typically occurs during cooking. However, studies using animal models and population trials have suggested that human gut bacteria might act like an 'organ' in that they can secrete their own myrosinase. In this review, the hydrolysis of GLS by myrosinase is discussed, with an important focus on the gut microflora and their myrosinase-producing roles. © 2017 Society of Chemical Industry.

Kinetic and structural study of broccoli myrosinase and its interaction with different glucosinolates

Myrosinase is a glycosylated enzyme present in the Brassicaceae family that catalyzes the hydrolysis of glucoraphanin to yield sulforaphane, recognized as a health-promoting compound found in cruciferous foods. Broccoli myrosinase has been poorly characterized. In this work, the enzyme was purified from broccoli florets and its kinetic behaviour was analyzed. The cDNA of broccoli myrosinase was isolated and sequenced to obtain the amino acids sequence of the enzyme. A three-dimensional structural model of a broccoli myrosinase subunit was built and used to perform molecular docking simulations with glucoraphanin and other glucosinolates. Kinetic data were adjusted to the Two-Binding Sites Model that describes substrate inhibition, obtaining R² higher than 97%. The docking simulations confirmed the existence of two substrate-binding sites in the monomer, and allowed identifying the residues that interact with the substrate in each site. Our findings will help to design strategies to better exploit the health-promoting properties of broccoli.