Effects of some inhibitors on linamarin biosynthesis by cassava plantlets in tissue culture
3
Issued Date
2024
Copyright Date
1993
Resource Type
Language
eng
File Type
application/pdf
No. of Pages/File Size
xi, 99 leaves : ill.
Access Rights
open access
Rights
ผลงานนี้เป็นลิขสิทธิ์ของมหาวิทยาลัยมหิดล ขอสงวนไว้สำหรับเพื่อการศึกษาเท่านั้น ต้องอ้างอิงแหล่งที่มา ห้ามดัดแปลงเนื้อหา และห้ามนำไปใช้เพื่อการค้า
Rights Holder(s)
Mahidol University
Bibliographic Citation
Thesis (M.Sc. (Biochemistry))--Mahidol University, 1993
Suggested Citation
Saipin Sanghirun Effects of some inhibitors on linamarin biosynthesis by cassava plantlets in tissue culture. Thesis (M.Sc. (Biochemistry))--Mahidol University, 1993. Retrieved from: https://repository.li.mahidol.ac.th/handle/123456789/99840
Title
Effects of some inhibitors on linamarin biosynthesis by cassava plantlets in tissue culture
Alternative Title(s)
ผลของสารยับยั้งบางตัวต่อการสังเคราะห์ลินามารินในพืชสำปะ หลังที่เพาะเลี้ยงด้วยวิธีเพาะเลี้ยงเนื้อเยื่อ
Author(s)
Abstract
Cyanogenic glucosides, mainly linamarin, in cassava cause cyanide toxicity related to cassava consumption. To eliminate this health hazard problem, a new variety free of the cyanogenic glucosides should be produced. In the present study, cassava plantlets in tissue culture were used to test whether the plantlets could grow normally when linamarin biosynthesis is inhibited. To do so, potential inhibitors of enzyme involved in the biosynthesis were first tested in vitro using soluble enzyme and tissue slices before final in vivo test in the cassava plantlets tissue culture. Five analogs of acetone cyanohydrin were found to completely inhibit the glucosyltransferase which catalyzed linamarin synthesis from acetone cyanohydrin. Pre-incubation experiment and kinetic analysis show that three analogs, isobutyraldehyde, 2-methyl-butyraldehyde and 2-methyl--2butanol, were competitive and reversible inhibitors. Although chlorobutanol exhibited reversible inhibition in the pre-incubation experiment, it caused an increase in both Km and V(,max) of acetone cyanohydrin. Isobutylamine was an irreversible inhibitor. The IC(,50) values of these five analogs were 0.0075, 0.02, 1.25, 12.0 and 26.5 mM, respectively. Incorporation of 14C-valine into linamarin using petiole slices from tissue cultured plantlets was completely inhibited by three analogs, chlorobutanol, 2-methylbutyraldehyde and isobutylamine, and partially inhibited by isobutyraldehyde and.2-methyl-2-butanol. The IC(,50) values were 0.9, 2.1, 2.9, 4.0 and 14 mM, respectively. Chlorpromazine and coumarin, two inhibitors of cytochrome P(,450) which were involved in the microsomal oxidation of valine into acetone cyanohydrin, also inhibited the radioactive incorporation. Their IC(,50) values were 0.5 and 1.0 mM, respectively. By using cassava plantlets in tissue culture, the linamarin synthesis was effectively inhibited while the growth was normal in the presence of 0.35-0.4 mM 2-methylbutyraldehyde, 0.5 mM chlorobutanol or 0.5 mM coumarin. On the contrary, 0.2 mM chlorpromazine caused retardation and abnormality of growth of the cassava plantlets without a significant decrease in the linamarin level while 0.5-1.0 mM isobutyraldehyde affected neither the growth nor the linamarin synthesis. The data suggested that cassava could grow normally when the linamarin synthesis was much suppressed.
Description
Biochemistry (Mahidol University 1993)
Degree Name
Master of Science
Degree Level
Master's degree
Degree Department
Faculty of Science
Degree Discipline
Biochemistry
Degree Grantor(s)
Mahidol University