Cytosolic Cysteine Synthase Switch Cysteine and Mimosine Production in <Emphasis Type="Italic">Leucaena leucocephala</Emphasis> |
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| Authors: | Md Harun-Ur-Rashid Hironori Iwasaki Shahanaz Parveen Shigeki Oogai Masakazu Fukuta Md Amzad Hossain Toyoaki Anai Hirosuke Oku |
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| Institution: | 1.The United Graduate School of Agricultural Sciences,Kagoshima University,Kagoshima,Japan;2.Faculty of Agriculture,Sher-e-Bangla Agricultural University,Dhaka,Bangladesh;3.Tropical Biosphere Research Center,University of the Ryukyus,Okinawa,Japan;4.Graduate School of Agriculture,University of the Ryukyus,Okinawa,Japan;5.Department of Subtropical Biochemistry and Biotechnology, Faculty of Agriculture,University of the Ryukyus,Okinawa,Japan;6.Faculty of Agriculture,Saga University,Saga,Japan |
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| Abstract: | In higher plants, multiple copies of the cysteine synthase gene are present for cysteine biosynthesis. Some of these genes also have the potential to produce various kinds of β-substitute alanine. In the present study, we cloned a 1275-bp cDNA for cytosolic O-acetylserine(thiol)lyase (cysteine synthase) (Cy-OASTL) from Leucaena leucocephala. The purified protein product showed a dual function of cysteine and mimosine synthesis. Kinetics studies showed pH optima of 7.5 and 8.0, while temperature optima of 40 and 35 °C, respectively, for cysteine and mimosine synthesis. The kinetic parameters such as apparent Km, kcat were determined for both cysteine and mimosine synthesis with substrates O-acetylserine (OAS) and Na2S or 3-hydroxy-4-pyridone (3H4P). From the in vitro results with the common substrate OAS, the apparent kcat for Cys production is over sixfold higher than mimosine synthesis and the apparent Km is 3.7 times lower, suggesting Cys synthesis is the favored pathway. |
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