Cabbages, enzyme from

Finally, although the All desaturase from cabbage looper is probably the most studied enzyme involved in these pathways, much more work should be done with it and related enzymes. For example, it only produces Z products and does not function efficiently with 14 carbon substrates, indicating a fundamental difference with the enzyme from redbanded leafroller moths, which desaturates 14-carbon acids to give a mixture of Z and E product (22). Projects such as this may well prove technically difficult, but will provide great insight into the enzymatic mechanisms. 

In higher plants, although spermidine synthase activity has been detected in L. sativus (Suresh and Adiga, 1977), Vinca rosea (Baxter and Coscia, 1973), spinach (Sindhu and Cohen, 1984), and oat (Tiburcio et al., 1986a), the enzyme has been partially purified only from com (Hirasawa and Suzuki, 1983) and Chinese cabbage (Sindhu and Cohen, 1984 Yamanoha and Cohen, 1985). The com enzyme (pH optimum 7.2, Af, 43,000) was purified only 115-fold and was inhibited by thiol reagents (Hirasawa and Suzuki, 1983). The enzyme from Chinese cabbage (pH optimum 8.8, 81,000) was initially purified 160-fold... 

In contrast to pheromones that involve single complex compounds, many moth species have been found to utilize a specific blend of relatively simple fatty acid-derived compounds. It appears that the evolution of a unique enzyme, A1 desaturase, used in combination with 2-carbon chain-shortening reactions (Figure 3) has allowed moth species to produce a variety of unsaturated acetates, aldehydes, and alcohols that can be combined in almost unlimited blends to impart species specificity. For example, biosynthetic precursors for the six-component pheromone blend of acetates for the cabbage looper moth (12) (Figure 2) can be determined easily from the cascade of acyl intermediates produced by the A11-desaturase and chain-shortening reactions (Figure 3). 

Blood and various organs of humans and other animals contain esterases capable of acetylsalicylic acid hydrolysis. A comparative study has shown that the liver is the most active tissue in all animal species studied except for the guinea pig, in which the kidney is more than twice as active as the liver. Human liver is least active the enzyme in guinea pig liver is the most active. The relatively low toxicity of some of the new synthetic pyrethroid insecticides appears to be related to the ability of mammals to hydrolyze their carboxyester linkages. Thus mouse liver microsomes catalyzing (+)-/runs-resin e 111ri n hydrolysis are more than 30-fold more active than insect microsomal preparations. The relative rates of hydrolysis of this substrate in enzyme preparations from various species are mouse > > milkweed bug > > cockroach > > cabbage looper > housefly. 

Similarly, it has been shown that consumption of cruciferous vegetables is associated with a lower incidence of cancers. Induction of phase II enzymes such as the glutathione S-transferase (GST) and quinone reductase (QR) have been demonstrated in broccoli, cabbage, and brussel sprouts. Many natural isothiocyanates derived from cruciferous vegetables and some fruits have been shown to cause induction of phase II enzymes in cultured cells and rodents. 

The most common desaturase in most organisms, including insects, is stearoyl Co A desaturase, which introduces a double bond in the 9-10 position of long-chain fatty acids (2JL). Similarities between this enzyme and the All desaturase from cabbage looper include location in the microsomal fraction, lack of sensitivity to carbon monoxide, inhibition by cyanide, use of a reduced nicotine-adenine nucleotide cofactor as an electron source and use of 16 and 18 carbon acids as preferred substrates. 

One pragmatic approach to the problem is the flavorese concept (i). A crude enzyme preparation from the fresh food or a closely related species is added to the processed food in the hope that the nonvolatile flavor precursors are still present and will yield the full range of fresh flavor components upon enzymatic treatment. This approach has been applied with some success to watercress (1,2), cabbage 1,2, 3, 4), horseradish 2, 3), onions 2, 3), carrots 2, 3, 5), peas, beans 2,3,6), citrus juice (2, 7), raspberries (8), tomato juice (2, 3, 9), bananas (JO), and various flower fragrances 11). This would seem to be a desirable approach since the products of different enzymatic reactions are probably necessary for full flavor. However the flavor-forming activity of the enzyme preparations was variable (5, 6, 7, 9), and the flavors were not always like that of the fresh vegetable (3). The several enzymes and flavor precursors may not have been present in the normal ratios. Also, to be practical, the enzyme preparation must be inexpensive to prepare and store, the substrates must persist in the processed food, and they must be available to enzyme action. One also wonders how processed foods can be enzymatically treated under sterile conditions. 

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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