Sinapis phylogeny and evolution of glucosinolates and specific nitrile degrading enzymes

• Published in: Phytochemistry (Oxford) Vol. 69; no. 17; pp. 2937 - 2949
• Main Authors: Agerbirk, Niels, Warwick, Suzanne I., Hansen, Paul R., Olsen, Carl E.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier Ltd 01.12.2008; Elsevier
• Subjects: 4-hydroxyphenylacetonitrile; aminohydrolases; Aminohydrolases - metabolism; aromatic hydrocarbons; Biological and medical sciences; Branched-chain glucosinolate; Brassica; Brassicaceae; Chemical constitution; chemotaxonomy; Coincya; enzyme activity; Evolution; Evolution, Molecular; Fundamental and applied biological sciences. Psychology; Glucosinolate; glucosinolates; Glucosinolates - chemistry; Glucosinolates - genetics; Glucosinolates - metabolism; Homosinalbin; hydro-lyases; Hydro-Lyases - metabolism; hydrolases; Kremeriella; Metabolism; Molecular Structure; Nitrilase; nitrilases; Nitrile hydratase; Nitrile specifier protein; nitriles; Nitriles - metabolism; Phylogeny; Plant Leaves - chemistry; Plant physiology and development; Sinalbin; Sinapis; Sinapis - genetics; Sinapis alba; Sinapis arvensis; Sinapis pubescens; Sorghum; Sorghum bicolor; Species Specificity; Substrate Specificity; Kremeriella; Glucosinolate; Nitrile specifier protein; Homosinalbin; Sorghum; Sinalbin; Metabolism; Branched-chain glucosinolate; Brassica; Nitrile hydratase; Evolution; Coincya; Sinapis; Nitrilase; Monocotyledones; Lyases; Phylogeny; Branched chain; Cruciferae; Gramineae; Dicotyledones; Angiospermae; Enzyme; Chemical structure; Protein; Plant origin; Hydrolases; Herbaceous plant; Spermatophyta; Pharmacokinetics; Carbon-oxygen lyases; Hydro-lyases
• ISSN: 0031-9422; 1873-3700
• DOI: 10.1016/j.phytochem.2008.08.014

The crucifers Sinapis alba and Sinapis arvensis are distantly related but both contain 4-hydroxybenzylglucosinolate (sinalbin) and enzymatic activity converting the corresponding nitrile to amide and carboxylic acid. Distribution of 4-hydroxyphenylacetonitrile degrading activity and 27 glucosinolates in the genus Sinapis and related species is presented. The specificity of the reaction and low nitrile degrading activity in related species both with and without sinalbin, suggest a facultative metabolic connection with sinalbin that evolved twice. Levels of sinalbin (4-hydroxybenzylglucosinolate) and 28 other glucosinolates were determined in leaves and roots of 20 species that were either phylogenetically close to Sinapis alba, Sinapis arvensis, or Sinapis pubescens (tribe Brassiceae, Brassicaceae), or were expected to contain arylalkyl nitrilase activity. Comparison with a molecular phylogenetic tree based on ITS DNA sequences identified two separate occurrences of sinalbin. The first in a group of species related to S. alba (including members of the genera Coincya and Kremeriella); and the second in S. arvensis, nested among sinalbin deficient species. Significant 4-hydroxyphenylacetonitrile degrading enzyme activity was found in both S. alba and S. arvensis, but in S. alba the major product was the corresponding carboxylic acid, while in S. arvensis the major product was the amide. Both investigated enzyme activities, nitrilase and nitrile hydratase, were specific, accepting only certain arylacetonitriles such as 4-hydroxy and 4-methoxyphenylacetonitrile. Only the S. alba enzyme required an oxygen in para position of the substrate, as found in sinalbin. Indole-3-acetonitrile, arylcyanides, and arylpropionitriles were poor substrates. The nitrilase activity of S. alba was quantitatively comparable to that reported in the monocot Sorghum bicolor (believed to be involved in cyanogenic glycoside metabolism). Glucosinolates derived from methionine were found in all Sinapis clades. Glucosinolate patterns suggested a complex evolution of glucosinolates in the investigated species, with several apparent examples of abrupt changes in glucosinolate profiles including chain length variation and appearance of glucosinolates derived from branched-chain amino acids. NMR data for desulfated homosinalbin, 9-methylsulphonylnonylglucosinolate, 3-methylpentylglucosinolate and related glucosinolates are reported, and a facultative connection between sinalbin and specific nitrilases is suggested.