Enzyme allium flavor

S Alkylcysteine Sulfoxide Lyase (alliinase), the Allium Flavor Enzyme... 

Members of the genus Allium (onion, garlic, leeks, etc.) provide a powerful example of an enzyme which distinguishes itself. Though there are hundreds of detectable enzymes occurring naturally in foods, it is difficult to find many examples where an individual enzyme is predominately responsible for a phenomenon. Enzymes and enzyme systems are responsible for the very identity of the food product. It is the enzyme composition that determines the flavor attributes and the textural differences in firmness, as well as the general appearance and color of food items. Table II provides examples of cases where particular changes in food can be primarily ascribed to a specific enzyme or enzyme system. 

Onions Allium cepa) were shown to contain similar compounds, S-methyl and S-propyl-L-cysteine sulfoxide (20). The principal flavor precursor in onion is fmn -S( + )-l-propenyl-L-cysteine sulfoxide 21, 22, 23). It is responsible for the lachrymatory properties and bitter taste of freshly cut onion (22). All these compounds were cleaved by an S-alkyl-L-cysteine sulfoxide lyase from onion 24, 25) which yielded pyruvate and ammonia in addition to a sulfur compound. The enzyme has also been demonstrated in Bacillus subtilis 26) and in a number of the Cruciferae where the only substrate known is S-methyl-L-cysteine sulfoxide (27). The product presumably gives rise to dimethyl disulfide which is the odor of cooked cabbage. 

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