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Plant Sci

Title:		"Biochemical characteristics of a novel vegetative tissue geraniol acetyltransferase from a monoterpene oil grass (Palmarosa, Cymbopogon martinii var. Motia) leaf"
Author(s):		Sharma PK; Sangwan NS; Bose SK; Sangwan RS;
Address:		"Central Institute of Medicinal and Aromatic Plants (CSIR), P.O. CIMAP, Lucknow 226015, UP, India"
Journal Title:		Plant Sci
Year:		2013
Volume:		20121229
Issue:
Page Number:		63 - 73
DOI:		10.1016/j.plantsci.2012.12.013
ISSN/ISBN:		1873-2259 (Electronic) 0168-9452 (Linking)
Abstract:		"Plants synthesize volatile alcohol esters on environmental insult or as metabolic induction during flower/fruit development. However, essential oil plants constitutively produce them as the oil constituents. Their synthesis is catalyzed by BAHD family enzymes called alcohol acyltransferases (AATs). However, no AAT has been characterized from plant foliage synthesizing acyclic monoterpenoids containing essential oils. Therefore, we have purified and biochemically characterized a geraniol: acetyl coenzyme A acetyltransferase (GAAT) from Palmarosa aroma grass (Cymbopogon martinii) leaf. MALDI-assisted proteomic study of the 43kDa monomeric enzyme revealed its sequence motif novelties e.g. relaxed conservation at Phe and Trp in DFGWG'. This suggests permissiveness of variations in the conserved motif without loss of catalytic ability. Also, some new conserved/semi-conserved motifs of AATs were recognized. The GAAT k(cat)/K(m) values (300-700M(-1)s(-1)) were low (a generic characteristic for secondary metabolism enzyme) but higher than those of some floral AATs. Wide substrate acceptability for catalyzing acetylation of diverse primary alcohols (chain of >/=C(6)) implied its catalytic description as a 'primary aliphatic alcohol acetyltransferase'. It signifies metabolic ability to deliver diverse aroma esters, should the acceptor alcohols be available in planta. To our knowledge, this is the first report of detailed kinetics of a vegetal monoterpenol acyltransferase"
Keywords:		"Acetyltransferases/chemistry/*isolation & purification/metabolism Acyclic Monoterpenes Cymbopogon/chemistry/*enzymology Esters Hydrogen-Ion Concentration Kinetics Monoterpenes/metabolism Oils, Volatile/*metabolism Organ Specificity Plant Leaves/chemistry/;"
Notes:		"MedlineSharma, Pankaj K Sangwan, Neelam S Bose, Subir K Sangwan, Rajender S eng Research Support, Non-U.S. Gov't Ireland 2013/02/19 Plant Sci. 2013 Apr; 203-204:63-73. doi: 10.1016/j.plantsci.2012.12.013. Epub 2012 Dec 29"