The biosynthesis of canavanine from14CO2and its asymmetric labeling in isolated pericarp, tissue ofCanavalia ensiformis
✍ Scribed by Richard P. Warren; Gordon E. Hunt
- Book ID
- 104750505
- Publisher
- Springer-Verlag
- Year
- 1971
- Tongue
- English
- Weight
- 379 KB
- Volume
- 100
- Category
- Article
- ISSN
- 0032-0935
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✦ Synopsis
Pericarp disks from the fruit of the jackbean (Canavalia ensi/ormis) when exposed to ~4C02 for 2 days carried out photosynthesis and the canavanine extracted from the tissue was labeled with the radioisotope. ~Vhen beef liver arginase was allowed to react with this canavanine the products were homoserine, canaline, urea and an unknown compound. The activity ratio of C4:C ~ compounds was close to 2:1. No label could be detected in the canavanine from leaves exposed in the same way to ltC02 and it was concluded that normally canavanine synthesis occurs in the pericarp chlorenchyma.
Although the amino acid canavanine was discovered in 1929 by Kitagawa and Tomiya, its pathway of synthesis is still unknown. Typical suggestions of its degradation are those of Johnston (1956) who found high concentrations of homoserine in the germinating seedling ; he found that cotyledon tissue incubated with canavanine also yielded homoserine. He concluded canavanine was normally broken down by hydrolysis and reduction of the resulting canaline to homoserine. Rosenthal (1970) more recently carried out similar experiments with jackbean cotyledons and found little homoscrine but large amounts of canaline. The characteristics of several enzyme systems attacking canavanine in microorganisms were summarized by Kalyankar et al. (1964); possible products of canavanine cleavage werehomoserine, and guanidine (Streptococcus ]aecalis), o-ureidohomoserine and ammonia (S./aecalis), homoserine and hydroxyguanidine (Pseudomonas spee.), and ~-keto-o-gu~ndidylhydroxybutyric acid and ammonia (Neurospora erassa). Studies by Bledsoe (1964), Nakatu et al. (1964) and tto and Shen (1966), made in an effort to show the organ or tissue in which the amino acid was synthesized in plants, indicated in Canavalia spec. that the