An insight into the sequential, structural and phylogenetic properties of banana 1-aminocyclopropane-1-carboxylate synthase 1 and study of its interaction with pyridoxal-5′-phosphate and aminoethoxyvinylglycine

Abstract

In banana, ethylene production for ripening is accompanied by a dramatic increase in 1-aminocyclopropane-1-carboxylate (ACC) content, transcript level of Musa acuminata ACC synthase 1 (MA-ACS1) and the enzymatic activity of ACC synthase 1 at the onset of the climacteric period. MA-ACS1 catalyses the conversion of S-adenosyl-L-methionine (SAM) to ACC, the key regulatory step in ethylene biosynthesis. Multiple sequence alignments of 1-aminocyclopropane-1-carboxylate synthase (ACS) amino acid sequences based on database searches have indicated that MA-ACS1 is a highly conserved protein across the plant kingdom. This report describes an in silico analysis to provide the first important insightful information about the sequential, structural and phylogenetic characteristics of MA-ACS1. The three-dimensional structure of MA-ACS1, constructed based on homology modelling, in combination with the available data enabled a comparative mechanistic analysis of MA-ACS1 to explain the catalytic roles of the conserved and non-conserved active site residues. We have further demonstrated that, as in apple and tomato, banana- ACS1 (MA-ACS1) forms a homodimer and a complex with cofactor pyridoxal-5'-phosphate (PLP) and inhibitor aminoethoxyvinylglycine (AVG). We have also predicted that the residues from the PLP-binding pocket, essential for ligand binding, are mostly conserved across the MA-ACS1 structure and the competitive inhibitor AVG binds at a location adjacent to PLP.

Effect of aminoethoxyvinylglycine and 1-methylcyclopropene on leaf abscission and root formation in Corymbia and Eucalyptus cuttings

“…In contrast, MCP does not affect root length, root weight or shoot length of E. pinnatum cuttings (Müller et al, 1997), nor does it affect root length or root weight of Dendranthema grandiflorum, Hibiscus rosa-sinensis or P. zonale cuttings (Serek et al, 1998). AVG inhibits a key ethylene biosynthesis enzyme, ACC synthase, which catalyses the conversion of Sadenosylmethionine (SAM) to 1-aminocyclopropane-1-carboxylic acid (ACC) (Martínez-Romero et al, 2007;Choudhury et al, 2010). AVG could inhibit growth by causing the accumulation of SAM, its precursors such as methionine, or its other derivatives such as putrescine, spermidine and spermine (Arigita et al, 2004;Martínez-Romero et al, 2007).…”

Vitamin B6 and Its Role in Cell Metabolism and Physiology

“…The function of PLP-dependent enzymes in amino acid metabolism also has significant indirect impacts on secondary metabolites that depend on amino acids as their precursors. For example, this is the case for some plant hormones (phytohormones) such as ethylene, auxin, or cytokinin [ 5 , 121 , 122 , 123 ]. Auxin biosynthesis requires a tryptophan aminotransferase that catalyzes the step to indole-3-pyruvate, an immediate precursor of the auxin indole-3-acetic acid from L-tryptophan and 2-oxoglutarate [ 122 ].…”

“…Since its discovery in 1934 by György and colleagues [ 2 ], it has been implicated as a co-factor in more than 140 biochemical reactions in the cell [ 3 ]. Although most vitB 6 co-catalyzed reactions are related to amino acid biosynthesis and catabolism, vitB 6 also contributes to fatty acid biosynthesis, breakdown of certain storage compounds in animals and plants, as well as in the biosynthesis of plant hormones, neurotransmitters, and organelle-specific compounds such as chlorophyll [ 4 , 5 , 6 , 7 , 8 , 9 , 10 ]. In addition, vitB 6 can quench reactive oxygen species (ROS) [ 11 ].…”

Temporal and spatial control of gene expression in horticultural crops

“… 102 , 103 Promoters from genes such as the ACC ox idase and ACO synthase isoforms that catalyze the key steps in ethylene biosynthesis have also been analyzed in a number of plant species to identify specific cis- elements involved in the regulatory process. 104–106 Deletion analysis of a peach ACC oxidase promoter fused to the GUS gene revealed the presence of regulatory regions that controlled gene expression at specific stages of fruit ripening. 107 Longer sequences of the promoter enhanced GUS expression in transgenic tomato, which was attributed to the presence of an enhancer element.…”