Thioglucosidases

Fig. 1. Scheme of mechanism-based principle of transglycosyldation with (A) an inverting /5-glycosi-dase, (B) a retaining thioglucosidase, and (C) an inverting thioglycosynthase. 

Myrosinase has thioglucosidase activity. The myrosinase-mediated degradation of glucolimnanthin yields an intermediate aglycone that rearranges to form... 

Enzyme preparations of three Pieris species each contained B-thioglucosidase activity, a fact previously reported (36), and each inhibited hydrolysis in one or more combinations with a plant enzyme-substrate system. These data are being quantified and extended to include insect/preferred host-plant pairs. 

Scheme 7.4 Products of thioglucosidase (myrosinase) hydrolysis of glucosinolates. Volatile iso-thiocyantes and their corresponding nitriles are important flavoirr compounds, in particular in vegetables of the cabbage family. At low pH the formation of nitrile is favoured, whereas neutral or high pH favours the formation of the isothiocyanate...

TANG, C.S., Localization of benzyl glucosinolate and thioglucosidase in Carica papaya fruit., Phytochemistry, 1973,12, 769-773. 

In conclusion, it seems that myrosinase activity is relatively easy (in evolutionary time) to acquire from p-glucosidases. It will be a fascinating challenge to pin down the exact molecular alterations that are responsible for the transition from P-[OJ-glucosidase to p-[S]-thioglucosidase. 

Glucosinolates such as sinigrin are molecules that consist of a /3-thioglucose moiety, a sulfonated oxime, and a variable side chain derived from various amino acids (Figure 5).43 44 Glucosinolates themselves are not toxic to herbivores and are widely distributed in plant tissues. On the contrary, the enzyme called myrosinase or thioglucosidase is distributed in myrosin cells that do not contain glucosinolates. In the flower stalk of... 

Indolyl-, alkyl- indolyl isothiocynates from glucosinolates via myrosinase (thioglucosidase)... 

Alexine (1) and 3-ep/-anstraline (10) are generally poor inhibitors of glncosidases and galactosidases/ bnt they display amyloglncosidase inhibition comparable with that of castanospermine, while 1 is an effective thioglucosidase inhibitor. The configurational and conformational analyses of alexines nsing NMR data and X-ray have been well docnmented. ... 

Glucosinolates are p-S-glucosides of isothiocyanates (ITC). They are non-volatile, water-soluble compounds, cleaved by the enzyme myrosinase, a P-thioglucosidase, when plant tissues are damaged to form isothiocyanates (mustard oils). 

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