{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,22]],"date-time":"2026-10-22T21:27:32Z","timestamp":1792704452206,"version":"4.5.0"},"reference-count":35,"publisher":"Oxford University Press (OUP)","issue":"2","license":[{"start":{"date-parts":[[1999,6,1]],"date-time":"1999-06-01T00:00:00Z","timestamp":928195200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/academic.oup.com\/journals\/pages\/open_access\/funder_policies\/chorus\/standard_publication_model"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"published-print":{"date-parts":[[1999,6,1]]},"abstract":"<jats:title>Abstract<\/jats:title><jats:p>Caffeine synthase (CS), theS-adenosylmethionine-dependentN-methyltransferase involved in the last two steps of caffeine biosynthesis, was extracted from young tea (Camellia sinensis) leaves; the CS was purified 520-fold to apparent homogeneity and a final specific activity of 5.7 nkat mg\u22121protein by ammonium sulfate fractionation and hydroxyapatite, anion-exchange, adenosine-agarose, and gel-filtration chromatography. The native enzyme was monomeric with an apparent molecular mass of 61 kD as estimated by gel-filtration chromatography and 41 kD as analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The enzyme displayed a sharp pH optimum of 8.5. The final preparation exhibited 3- and 1-N-methyltransferase activity with a broad substrate specificity, showing high activity toward paraxanthine, 7-methylxanthine, and theobromine and low activity with 3-methylxanthine and 1-methylxanthine. However, the enzyme had no 7-N-methyltransferase activity toward xanthosine and xanthosine 5\u2032-monophosphate. The Km values of CS for paraxanthine, theobromine, 7-methylxanthine, andS-adenosylmethionine were 24, 186, 344, and 21 \u03bcm, respectively. The possible role and regulation of CS in purine alkaloid biosynthesis in tea leaves are discussed. The 20-amino acid N-terminal sequence for CS showed little homology with other methyltransferases.<\/jats:p>","DOI":"10.1104\/pp.120.2.579","type":"journal-article","created":{"date-parts":[[2002,7,27]],"date-time":"2002-07-27T05:00:20Z","timestamp":1027746020000},"page":"579-586","source":"Crossref","is-referenced-by-count":94,"title":["Purification and Characterization of Caffeine Synthase from Tea Leaves1"],"prefix":"10.1093","volume":"120","author":[{"given":"Misako","family":"Kato","sequence":"first","affiliation":[{"name":"Department of Biology, Faculty of Science, Ochanomizu University, Tokyo 112\u20138610, Japan (M.K., H.A.)"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Kouichi","family":"Mizuno","sequence":"additional","affiliation":[{"name":"Institute of Agricultural and Forest Engineering, University of Tsukuba, Ibaraki 305\u20138572, Japan (K.M., T.F.)"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Tatsuhito","family":"Fujimura","sequence":"additional","affiliation":[{"name":"Institute of Agricultural and Forest Engineering, University of Tsukuba, Ibaraki 305\u20138572, Japan (K.M., T.F.)"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Masanori","family":"Iwama","sequence":"additional","affiliation":[{"name":"Department of Microbiology, Hoshi College of Pharmacy, Ebara, Tokyo 142\u20130063, Japan (M. Iwama, M. Irie)"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Masachika","family":"Irie","sequence":"additional","affiliation":[{"name":"Department of Microbiology, Hoshi College of Pharmacy, Ebara, Tokyo 142\u20130063, Japan (M. Iwama, M. Irie)"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Alan","family":"Crozier","sequence":"additional","affiliation":[{"name":"Division of Biochemistry and Molecular Biology, Institute of Biomedical and Life Sciences, University of Glasgow, Glasgow G12 8QQ, United Kingdom (A.C.)"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Hiroshi","family":"Ashihara","sequence":"additional","affiliation":[{"name":"Department of Biology, Faculty of Science, Ochanomizu University, Tokyo 112\u20138610, Japan (M.K., H.A.)"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"286","published-online":{"date-parts":[[1999,6,1]]},"reference":[{"key":"2021050312144397700_R1","first-page":"117","article-title":"Biosynthesis and metabolism of caffeine and related purine alkaloids in plants.","volume-title":"Advances in Botanical Research, Vol 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