Accepted name: 2,4-dihydroxy-7-methoxy-2H-1,4-benzoxazin-3(4H)-one 2-D-glucosyltransferase
Reaction: (1) UDP-α-D-glucose + 2,4-dihydroxy-7-methoxy-2H-1,4-benzoxazin-3(4H)-one = UDP + (2R)-4-hydroxy-7-methoxy-3-oxo-3,4-dihydro-2H-1,4-benzoxazin-2-yl β-D-glucopyranoside
(2) UDP-α-D-glucose + 2,4-dihydroxy-2H-1,4-benzoxazin-3(4H)-one = UDP + (2R)-4-hydroxy-3-oxo-3,4-dihydro-2H-1,4-benzoxazin-2-yl β-D-glucopyranoside
Glossary: 2,4-dihydroxy-2H-1,4-benzoxazin-3(4H)-one = DIBOA
2,4-dihydroxy-7-methoxy-2H-1,4-benzoxazin-3(4H)-one = DIMBOA
(2R)-4-hydroxy-3-oxo-3,4-dihydro-2H-1,4-benzoxazin-2-yl β-D-glucopyranoside = DIBOA β-D-glucoside
(2R)-4-hydroxy-7-methoxy-3-oxo-3,4-dihydro-2H-1,4-benzoxazin-2-yl β-D-glucopyranoside = DIMBOA β-D-glucoside
Other name(s): uridine diphosphoglucose-2,4-dihydroxy-7-methoxy-2H-1,4-benzoxazin-3(4H)-one 2-glucosyltransferase; BX8; BX9; benzoxazinoid glucosyltransferase; DIMBOA glucosyltransferase
Systematic name: UDP-α-D-glucose:2,4-dihydroxy-7-methoxy-2H-1,4-benzoxazin-3(4H)-one 2-β-D-glucosyltransferase
Comments: The enzyme is involved in the detoxification of the benzoxazinoids DIBOA (2,4-dihydroxy-2H-1,4-benzoxazin-3(4H)-one) and DIMBOA (2,4-dihydroxy-7-methoxy-2H-1,4-benzoxazin-3(4H)-one) which are stored as the respective non-toxic glucosides in the vacuoles in some plants, most commonly from the family of Poaceae (grasses). Benzoxazinoids are known to exhibit antimicrobial, antifeedant, and antiinsecticidal effects and are involved in the interaction of plants with other plants, insects, or microorganisms.
1.  Bailey, B.A. and Larson, R.L. Hydroxamic acid glucosyltransferases from maize seedlings. Plant Physiol. 90 (1989) 1071–1076. [PMID: 16666853]
2.  von Rad, U., Huttl, R., Lottspeich, F., Gierl, A. and Frey, M. Two glucosyltransferases are involved in detoxification of benzoxazinoids in maize. Plant J. 28 (2001) 633–642. [PMID: 11851909]
[EC created 1992, modified 2012]
Accepted name: 4-hydroxy-7-methoxy-3-oxo-3,4-dihydro-2H-1,4-benzoxazin-2-yl glucoside β-D-glucosidase
Reaction: (1) (2R)-4-hydroxy-7-methoxy-3-oxo-3,4-dihydro-2H-1,4-benzoxazin-2-yl β-D-glucopyranoside + H2O = 2,4-dihydroxy-7-methoxy-2H-1,4-benzoxazin-3(4H)-one + D-glucose
(2) (2R)-4-hydroxy-3-oxo-3,4-dihydro-2H-1,4-benzoxazin-2-yl β-D-glucopyranoside + H2O = 2,4-dihydroxy-2H-1,4-benzoxazin-3(4H)-one + D-glucose
Glossary: DIMBOA glucoside = (2R)-4-hydroxy-7-methoxy-3-oxo-3,4-dihydro-2H-1,4-benzoxazin-2-yl β-D-glucopyranoside
DIBOA glucoside = (2R)-4-hydroxy-3-oxo-3,4-dihydro-2H-1,4-benzoxazin-2-yl β-D-glucopyranoside
Other name(s): DIMBOAGlc hydrolase; DIMBOA glucosidase
Systematic name: (2R)-4-hydroxy-7-methoxy-3-oxo-3,4-dihydro-2H-1,4-benzoxazin-2-yl β-D-glucopyranoside β-D-glucosidase
Comments: The enzyme from Triticum aestivum (wheat) has a higher affinity for DIMBOA glucoside than DIBOA glucoside. With Secale cereale (rye) the preference is reversed.
1.  Sue, M., Ishihara, A. and Iwamura, H. Purification and characterization of a hydroxamic acid glucoside β-glucosidase from wheat (Triticum aestivum L.) seedlings. Planta 210 (2000) 432–438. [PMID: 10750901]
2.  Sue, M., Ishihara, A. and Iwamura, H. Purification and characterization of a β-glucosidase from rye (Secale cereale L.) seedlings. Plant Sci. 155 (2000) 67–74. [PMID: 10773341]
3.  Czjzek, M., Cicek, M., Zamboni, V., Bevan, D.R., Henrissat, B. and Esen, A. The mechanism of substrate (aglycone) specificity in β-glucosidases is revealed by crystal structures of mutant maize β-glucosidase-DIMBOA, -DIMBOAGlc, and -dhurrin complexes. Proc. Natl. Acad. Sci. USA 97 (2000) 13555–13560. [PMID: 11106394]
4.  Nikus, J., Esen, A. and Jonsson, L.M.V. Cloning of a plastidic rye (Secale cereale) β-glucosidase cDNA and its expression in Escherichia coli. Physiol. Plantarum 118 (2003) 337–348.
5.  Sue, M., Yamazaki, K., Yajima, S., Nomura, T., Matsukawa, T., Iwamura, H. and Miyamoto, T. Molecular and structural characterization of hexameric β-D-glucosidases in wheat and rye. Plant Physiol. 141 (2006) 1237–1247. [PMID: 16751439]
6.  Sue, M., Nakamura, C., Miyamoto, T. and Yajima, S. Active-site architecture of benzoxazinone-glucoside β-D-glucosidases in Triticeae. Plant Sci. 180 (2011) 268–275. [PMID: 21421370]
[EC created 2012]
Accepted name: indole-3-glycerol-phosphate lyase
Reaction: (1S,2R)-1-C-(indol-3-yl)glycerol 3-phosphate = indole + D-glyceraldehyde 3-phosphate
Other name(s): tryptophan synthase α; TSA; indoleglycerolphosphate aldolase; indole glycerol phosphate hydrolase; indole synthase; indole-3-glycerolphosphate D-glyceraldehyde-3-phosphate-lyase; indole-3-glycerol phosphate lyase; IGL; BX1; (1S,2R)-1-C-(indol-3-yl)glycerol 3-phosphate D-glyceraldehyde-3-phosphate-lyase
Systematic name: (1S,2R)-1-C-(indol-3-yl)glycerol-3-phosphate D-glyceraldehyde-3-phosphate-lyase (indole-forming)
Comments: Forms part of the defence mechanism against insects and microbial pathogens in the grass family, Gramineae, where it catalyses the first committed step in the formation of the cyclic hydroxamic acids 2,4-dihydroxy-2H-1,4-benzoxazin-3(4H)-one (DIBOA) and 2,4-dihydroxy-7-methoxy-2H-1,4-benzoxazin-3(4H)-one (DIMBOA) [1]. This enzyme resembles the α-subunit of EC, tryptophan synthase [3], for which, (1S,2R)-1-C-(indol-3-yl)glycerol 3-phosphate is also a substrate, but, unlike tryptophan synthase, its activity is independent of the β-subunit and free indole is released [2].
1.  Yanofsky, C. The enzymatic conversion of anthranilic acid to indole. J. Biol. Chem. 223 (1956) 171–184. [PMID: 13376586]
2.  Frey, M., Chomet, P., Glawischnig, E., Stettner, C., Grün, S., Winklmair, A., Eisenreich, W., Bacher, A., Meeley, R.B., Briggs, S.P., Simcox, K. and Gierl, A. Analysis of a chemical plant defense mechanism in grasses. Science 277 (1997) 696–699. [PMID: 9235894]
3.  Frey, M., Stettner, C., Paré, P.W., Schmelz, E.A., Tumlinson, J.H. and Gierl, A. An herbivore elicitor activates the gene for indole emission in maize. Proc. Natl. Acad. Sci. USA 97 (2000) 14801–14806. [PMID: 11106389]
4.  Melanson, D., Chilton, M.D., Masters-Moore, D. and Chilton, W.S. A deletion in an indole synthase gene is responsible for the DIMBOA-deficient phenotype of bxbx maize. Proc. Natl. Acad. Sci. USA 94 (1997) 13345–13350. [PMID: 9371848]
[EC created 1961, deleted 1972, reinstated 2006]