Myrosinase Activity in Bacteria as Demonstrated by the Conversion of Progoitrin to Goitrin.

Abstract

Progoitrin is a thioglycoside present in high concentration in the seeds of most Brassicaceous plants and in the edible parts of some, particularly rutabaga and turnip. I t is hydrolyzed by enzymes (myrosinases) in these plants to yield goitrin, a potent antithyroid compound ( 1,2,3) (Fig. 1 ).Although it had been assumed for many years that hydrolysis of thioglycosides similar to progoitrin could be accomplished only through the action of myrosinase of plant origin, recent studies have indicated that this view is incorrect. Reese et aZ(4) reported that the fungus Aspergillus s y d m * produced a P-thioglycosidase (termed "sinigrinase") active on the mustard oil thioglycosides sinigrin, sinalbin, and progoitrin; however, the enzyme could not be obtained from other fungal genera or from the bacteria, Bacillus subtilis or Pseudomonas aeruginosa, which also were found to "consume" sinigrin on prolonged (14-day) incubation with this compound. Thioglycosidase activity hydrblyzing several purinyl thioglycosides has been reported by Goodman et aZ(5) to be widespread in mammalian species, and to occur in the microorganisms Tetrahymena pyriformis and Escherichia coli.Because of the possible importance of goitrin derived from commonly ingested vegetables in the production of human non-toxic goiter, studies were undertaken of the metabolic fate of pure crystalline progoitrin in man after oral ingestion. It was found that in such cases goitrin could be demonstrated * Supported by grants from U.S.P.H.S. in blood and urine(6). These results suggested that the conversion of progoitrin to goitrin might have been carried out by thioglycosidase activity of bacteria in the gastrointestinal tract. This hypothesis was reinforced by the finding that incubation of rat or human feces with progoitrin resulted in goitrin formation( 3 ) . This myrosinase activity in feces was destroyed by boiling, filtration, or sonoration, and was markedly reduced by prior oral administration of Amphotericin B and Neomycin(3), a regimen which has been shown to effect a striking decrease in viable fecal bacterial flora (7).The data reported here concern experiments on the isolation and identification of fecal bacteria with myrminase activity, comparison of such organisms with stock strains of various bacterial species, and conditions necessary for formation and activity of bacterial myrosinase.MateriaZs and methods. Progoitrin was prepared from rutabaga seed by the method of Greer (2). Bacterial cell suspensions were obtained by growing the organisms, unless otherwise stated, in nutrient broth containing 1 % glucose for 18 hours a t 37°C without shaking. The cells were harvested by centrifugation, washed once with water, and resuspended in water at a concentration between 1.0 and 2.0 mg bacterial nitrogen per ml. The cell suspensions were incubated with progoitrin and buffer at concentrations noted in the legends, in a total volume of 5.0 ml contained in 50 ml Erlenmeyer flasks which were shaken in a water bath at 37°C. Length

Thiouracil-Forming Bacteria Identified and Characterized upon Porcine In Vitro Digestion of Brassicaceae Feed

“…Similar results were obtained in gnotobiotic E. coli (EM0) mice fed rapeseed meal (64). Moreover, degradation of progoitrine, a precursor of goitrine (a natural thyeostat), by E. coli (65) and of the glucosinolate sinigrin by L. agilis (R16) (27) have also been described. Specifically in rodents, pigs, and chickens, L. reuteri is one of the dominant species in the gastrointestinal tract (66).…”

The Effect of Heat Treatment and Enzyme Hydrolysis of Rapeseed Meal on the Performance of Broiler Chickens

“…(Srivastava et al 1975 While Leeson et al (1978) The lack of stability of the non-hydroxy thionitriles (N1, N3) during processing and incubation with changing pH was observed in an earlier study (Paik et al 1980 (Fig. l) Paik et al (1980) showed that addition of Greer (1962) and Oginsky et al (1965 …”

The Efficiency of Mitochondria-Targeted Curcumin in Reducing Thyroid Mitochondrial Oxidative Damage

“…Escherichia coli produced antithyroid compounds in cell-free and broth cultures (21)(22)(23), Paracolon Bacillus has to produce an enzyme that converts progoitrin to goitrin (24). E.coli and Cholera produced an enterotoxin that stimulates cyclic AMP in the thyroid gland and produced antithyroid compound (25).…”