Biological formation of ethylene

Abstract

This review summarizes the structures, biochemical properties, and mechanisms of two major biological sources of ethylene, the ethylene-forming enzyme (EFE) and 1-aminocyclopropane-1-carboxylic acid (ACC) oxidase (ACCO). EFE is found in...

Functional stress responses in Glaucophyta: evidence of ethylene and abscisic acid functions inCyanophora paradoxa

“…The ACO proteins in plants are 2-oxoglutarate and Fe (II)-dependent dioxygenase domain (2OGD)-containing proteins (Kawai et al, 2014) that fall into three phylogenetic clusters, type 1-3 ACOs (Houben and Van de Poel, 2019). Flowering plant ACO proteins are distinct from ACO-like genes in other lineages, including their closest homologs in bryophytes, green algae, and amoebozoans, that may be considered type 4 ACOs given confirmation of their function (Hausinger et al, 2023; Houben and Van de Poel, 2019; Li et al, 2023). Plant ACOs have sequence and structural homology to the bacterial ethylene forming enzyme (EFE) that uses 2-oxoglutarate as a substrate to create ethylene, with the putative type-4 ACOs having a closer affinity to EFE than the seed plant ACOs (type 1-3) (Hausinger et al, 2023).…”

“…Flowering plant ACO proteins are distinct from ACO-like genes in other lineages, including their closest homologs in bryophytes, green algae, and amoebozoans, that may be considered type 4 ACOs given confirmation of their function (Hausinger et al, 2023; Houben and Van de Poel, 2019; Li et al, 2023). Plant ACOs have sequence and structural homology to the bacterial ethylene forming enzyme (EFE) that uses 2-oxoglutarate as a substrate to create ethylene, with the putative type-4 ACOs having a closer affinity to EFE than the seed plant ACOs (type 1-3) (Hausinger et al, 2023). Given the conservation of the active site between canonical ACOs and EFE, one intriguing possibility is that EFE and possibly type-4 ACOs have dual substrate specificity and can make ethylene from both ACC and 2-oxoglutarate, which could explain the presence of ACC oxidase activity in the absence of canonical ACO and ACS genes in lineages outside of flowering plants.…”

Structural, Spectroscopic, and Computational Insights from Canavanine-Bound and Two Catalytically Compromised Variants of the Ethylene-Forming Enzyme

“…4−7 In contrast, the minor reaction of guanidine/P5C formation is associated with the well-known hydroxylation chemistry of 2OG-dependent oxygenases that involves a ferryl intermediate. 1,8 The best characterized EFE is that from the Pseudomonas savastanoi (formerly Pseudomonas syringae) pv phaseolicola strain PK2, for which several crystal structures have been reported. 8−10 This enzyme binds mononuclear Fe(II) using three side chains (H189, D191, and H268) with three water molecules completing the six-coordinate geometry.…”

“…Some bacteria and fungi possess an Fe­(II), 2-oxoglutarate (2OG), and l -arginine ( l -Arg)-dependent oxygenase known as the ethylene-forming enzyme (EFE) that (1) cleaves three C–C bonds of 2OG to form ethylene and three molecules of CO 2 /bicarbonate and (2) catalyzes the oxidative decarboxylation of 2OG to form CO 2 and succinate coupled to the C5 hydroxylation of l -Arg, which decomposes to guanidine and l -Δ 1 -pyrroline-5-carboxylate (P5C) (Scheme ). , Computational and biochemical studies suggest that the bifurcated pathway splits at the level of an Fe­(III)·superoxo complex, with the major reaction, ethylene generation, requiring dioxygen insertion into the C1–C2 bond of 2OG, formation of a propionyl-3-yl radical and an Fe­(III)-bound carbonate, and their coupling followed by fragmentation to yield the target product. − In contrast, the minor reaction of guanidine/P5C formation is associated with the well-known hydroxylation chemistry of 2OG-dependent oxygenases that involves a ferryl intermediate. , …”

“… 4 − 7 In contrast, the minor reaction of guanidine/P5C formation is associated with the well-known hydroxylation chemistry of 2OG-dependent oxygenases that involves a ferryl intermediate. 1 , 8 …”