Purification and identification of linoleic acid hydroperoxides generated by soybean seed lipoxygenases 2 and 3

It has been known that lipoxygenase (LOX) isozymes exhibit differences in product formation, but most product information to date is for LOX 1 among soybean (Glycine max) LOX isozymes. In this study, LOXs 2 and 3 were purified and used to generate hydroperoxide (HPOD) products in an in vitro system using linoleic acid as a substrate in the presence of either air or O2. The products were analyzed to determine their stereoisomeric characteristics. The control (no enzyme) showed only low levels of hydroperoxide production and no stereoisomeric specificity. LOX 2 shows high specificity in product formation, producing roughly 4 times more 13-HPOD than 9-HPOD, nearly all of which was 13-S(Z,E)-HPOD. LOX 3 produced more 9-HPOD than 13-HPOD at approximately a 2:1 ratio. No single stereoisomer was predominant among LOX 3 products. These results demonstrate that different isozymes of LOX have characteristic product profiles in in vitro reactions.     

A simple and efficient system for green note compound biogenesis by use of certain lipoxygenase and hydroperoxide lyase sources

Six-carbon (C(6)) aldehydes and alcohols are important components of the aroma and flavor of fruits and vegetables. Soybean lipoxygenase (LOX) isozyme LOX 3 was reported not only to produce less 13-hydroperoxides, precursors of C(6) aldehydes, but also to convert them to ketodiene products. Here, we examined the effects of LOX 3 on hexenal formation from linolenic acid homogenized with watermelon 13-hydroperoxide lyase (HL)-overexpressing Nicotiana tabacum leaves and soybean acetone powder. Compared to the wild type, which contains LOXs 1, 2, and 3, the elimination of LOX 3 in LOX 1 + 2 facilitates greater production of hexenals. The use of LOX 2 alone yielded the highest hexenal production, while a two-step conversion was required for LOX 1 to produce hexenals at high levels due to different pH optima of the enzymes involved. These results clearly demonstrate that the soybeans lacking LOX 3 in combination with watermelon HL-overexpressing leaf tissues greatly enhance hexenal formation.     

Watermelon (Citrullus lanatus) hydroperoxide lyase greatly increases C6 aldehyde formation in transgenic leaves

Fatty acid hydroperoxide lyase (HL) is the key enzyme for the production of the "green note"compounds, leaf aldehyde [(2E)-hexenal] and leaf alcohol [(3Z)-hexenol], in plant tissues. A cDNA encoding HL was cloned from leaves of watermelon (Citrullus lanatus) and expressed in Nicotiana tabacum. The enzyme is 3 times more active with 13-hydroperoxylinolenic acid than with 13-hydroperoxylinoleic acid. The activity against 9-hydroperoxides of polyunsaturated fatty acids is minimal. Enzyme activity of the watermelon HL in the transgenic leaves was approximately 50 times higher than endogenous HL activity in the wild-type N. tabacum plants. When compared with Arabidopsis HL also expressed in N. tabacum, the highest HL activity is 10 times higher in watermelon HL overexpressing leaves than in Arabidopsis HL overexpressers.     

Effects of street landscape planting and urban public parks on dwelling environment evaluation in Japan

In this paper, we use data from 12 metropolitan cities in Japan to investigate the effects of street landscape planting and urban park areas on land prices, and estimate the magnitude and saturation levels of these effects, as well as examining the current level of planting and park areas in these cities. The empirical results imply that increasing the street landscape planting ratio improves the dwelling environment, in terms of both the magnitude and saturation level of the planting ratio, while increasing the amount of urban park area does not.