EC Number   |
General Information |
Reference |
|---|
   4.2.99.23 | evolution |
TCE enzymes belong to the carboxylesterase family in the alpha/beta-hydrolase fold superfamily, and specifically catalyze intramolecular transesterification, but not hydrolysis, functional diversity of carboxylesterases and related alpha/beta-hydrolase enzymes and proteins in plants, overview. TgTCEA1 and TgTCEB1 polypeptides show 52% identity to each other and approximately 40-45% identities to the sequences annotated as plant carboxylesterases. TgTCEs catalyze only intramolecular transesterification, while other plant carboxylesterases catalyze the hydrolysis of carboxylic esters to form carboxylic acids and alcohols. TgTCE polypeptides have sequence motifs typical of class I carboxylesterases in the alpha/beta-hydrolase fold superfamily, including the HGG motif. The two Gly residues in this motif are involved in the formation of an oxyanion hole structure during the formation of the acyl-enzyme complex. The other conserved motif is the catalytic triad Ser, Asp, and His, of which the catalytic Ser is present within the conserved pentapeptide sequence Gly-X-Ser-X-Gly |
747322 |
| 4.2.99.23 | physiological function |
tuliposide A converting enzyme (TCEA) and tuliposide B-converting enzyme (TCEB) catalyze intramolecular transesterification of 6-PosA and 6-PosB to form the corresponding lactones, PaA and PaB, respectively, and D-glucose. 6-PosA and 6-PosB serve as precursors of the corresponding alpha-methylene-gamma-butyrolactones, tulipalins A (PaA) and B (PaB), respectively, which are formed from the acyl group at the C-6 position. The 1alpha- and 1beta-anomers exist for 6-PosA/6-PosB and both anomers serve as substrates for TCEs. TCEA and TCEB catalyze the formation of PaA/1-PosA and PaB/1-PosA from PosD and PosF, respectively, by acting on the 6-acyl group of PosD and PosF. Neither enzyme acts on the 1-acyl group of PosD, PosF, or 1-PosA. Although intact tulip tissues constitutively accumulate large amounts of 6-Pos, biologically active PaA and PaB are far less abundant and are sometimes barely detectable, PaA and PaB are hardly detectable in intact plants. PaA and PaB respectively show antifungal and antibacterial activities, they are considered to be key secondary metabolites in the chemical defense of tulip, while 6-PosA and 6-PosB are considered to be storage forms of PaA and PaB, respectively. Enzyme TCEB shows lower overall activity than enzyme TCEA |
746803 |
| 4.2.99.23 | physiological function |
tuliposides (Pos) and tulipalins (Pa) are the major defensive secondary metabolites in tulip (Tulipa gesneriana). So far, seven analogues of Pos have been reported: 1-PosA, 1-PosB, 6-PosA, 6-PosB, PosD, PosE, and PosF, which differ in the number, position, and structure of the acyl side chain. They are categorized into monoacyl-glucose type (1-Pos and 6-Pos) and 1,6-diacyl-glucose type (PosD, PosE, and PosF), overview. The tuliposide-converting enzyme (TCE), a non-ester-hydrolyzing carboxylesterase, catalyzes the conversion of major defensive secondary metabolites, tuliposides, to antimicrobial tulipalins. PaA has been shown to have potent insecticidal activity against several insect pests, such as Thrips palmi. PaA functions as an antifungal agent rather than an antibacterial agent, and vice versa for PaB. Enzyme-mediated activation of postinhibitins |
747322 |
