ENSIKLOPEDIA

Caffeine synthase is a methyltransferase enzyme involved in the caffeine biosynthesis pathway. It is expressed in tea species, coffee species, and cocoa species. The enzyme catalyses three related reactions:^[1]^[2]

theobromine

+ SAM

caffeine

+ SAH

The first is the final methylation step in the biosynthesis of caffeine from xanthosine via theobromine. The methyl group comes from the cofactor, S-adenosyl methionine (SAM), which becomes S-adenosyl-L-homocysteine (SAH).^[3]

The second is the reaction which produces theobromine from 7-methylxanthine, a reaction also catalysed by theobromine synthase:^[3]

7-methylxanthine

+ SAM

theobromine

+ SAH

Finally, the enyme also converts paraxanthine to caffeine:^[2]

paraxanthine

+ SAM

caffeine

+ SAH

Caffeine synthase is expressed in the Camellia species irrawadiensis, ptilophylla, and sinensis;^[4] the Coffea species arabica,^[3]^[5] and canephora;^[6] and in Theobroma cacao.^[7]

References

↑ Kato M, Mizuno K, Fujimura T, Iwama M, Irie M, Crozier A, Ashihara H (June 1999). "Purification and characterization of caffeine synthase from tea leaves". Plant Physiol. 120 (2): 579–86. doi:10.1104/pp.120.2.579. PMC 59297. PMID 10364410.
1 2 Enzyme 2.1.1.160 at KEGG Pathway Database.
1 2 3 Uefuji H, Ogita S, Yamaguchi Y, Koizumi N, Sano H (May 2003). "Molecular cloning and functional characterization of three distinct N-methyltransferases involved in the caffeine biosynthetic pathway in coffee plants". Plant Physiol. 132 (1): 372–80. doi:10.1104/pp.102.019679. PMC 166982. PMID 12746542.
↑ Kato M, Mizuno K, Crozier A, Fujimura T, Ashihara H (August 2000). "Caffeine synthase gene from tea leaves" (PDF). Nature. 406 (6799): 956–7. doi:10.1038/35023072. PMID 10984041.
↑ Mizuno K, Okuda A, Kato M, Yoneyama N, Tanaka H, Ashihara H, Fujimura T (January 2003). "Isolation of a new dual-functional caffeine synthase gene encoding an enzyme for the conversion of 7-methylxanthine to caffeine from coffee (Coffea arabica L.)". FEBS Lett. 534 (1–3): 75–81. doi:10.1016/S0014-5793(02)03781-X. PMID 12527364.
↑ McCarthy AA, Biget L, Lin C, Petiard V, Tanksley SD, McCarthy JG (April 2007). "Cloning, expression, crystallization and preliminary X-ray analysis of the XMT and DXMT N-methyltransferases from Coffea canephora (robusta)". Acta Crystallographica Section F. 63 (Pt 4): 304–7. doi:10.1107/S1744309107009268. PMC 2330209. PMID 17401201.
↑ Yoneyama N, Morimoto H, Ye CX, Ashihara H, Mizuno K, Kato M (February 2006). "Substrate specificity of N-methyltransferase involved in purine alkaloids synthesis is dependent upon one amino acid residue of the enzyme". Mol. Genet. Genomics. 275 (2): 125–35. doi:10.1007/s00438-005-0070-z. PMID 16333668.

Transferase: one carbon transferases (EC 2.1)

2.1.1: Methyl-

N-	Histamine N-methyltransferase Phenylethanolamine N-methyltransferase Amine N-methyltransferase Phosphatidylethanolamine N-methyltransferase
O-	5-hydroxyindole-O-methyltransferase/Acetylserotonin O-methyltransferase Catechol-O-methyltransferase
Homocysteine	Betaine-homocysteine methyltransferase Homocysteine methyltransferase/Methionine synthase
Other	Phosphatidylethanolamine N-methyltransferase DNMT3B Histone methyltransferase Thymidylate synthase DNA methyltransferase Thiopurine methyltransferase Cyclopropane-fatty-acyl-phospholipid synthase

2.1.2: Hydroxymethyl-,
Formyl- and Related

Hydroxymethyltransferase	Serine hydroxymethyltransferase 3-methyl-2-oxobutanoate hydroxymethyltransferase
Formyltransferase	Phosphoribosylglycinamide formyltransferase Inosine monophosphate synthase
Other	Glutamate formimidoyltransferase Aminomethyltransferase

2.1.3: Carboxy-
and Carbamoyl

Carboxy	methylmalonyl-CoA carboxytransferase
Carbamoyl	Aspartate carbamoyltransferase Ornithine carbamoyltransferase Oxamate carbamoyltransferase Putrescine carbamoyltransferase 3-hydroxymethylcephem carbamoyltransferase Lysine carbamoyltransferase N-acetylornithine carbamoyltransferase

2.1.4: Amidine

Arginine:glycine amidinotransferase

v t e Enzymes
Activity	Active site Binding site Catalytic triad Oxyanion hole Enzyme promiscuity Diffusion-limited enzyme Cofactor Enzyme catalysis
Regulation	Allosteric regulation Cooperativity Enzyme inhibitor Enzyme activator
Classification	EC number Enzyme superfamily Enzyme family List of enzymes
Kinetics	Enzyme kinetics Eadie–Hofstee diagram Hanes–Woolf plot Lineweaver–Burk plot Michaelis–Menten kinetics
Types	EC1 Oxidoreductases (list) EC2 Transferases (list) EC3 Hydrolases (list) EC4 Lyases (list) EC5 Isomerases (list) EC6 Ligases (list) EC7 Translocases (list)

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