Biological formation of ethylene

Area of Science:

• Biochemistry
• Enzymology
• Plant Science

Background:

• Ethylene is a crucial plant hormone involved in various growth and stress responses.
• Two primary biological sources of ethylene are the ethylene-forming enzyme (EFE) in microbes and 1-aminocyclopropane-1-carboxylic acid (ACC) oxidase (ACCO) in plants.

Purpose of the Study:

• To review and compare the structures, biochemical properties, and reaction mechanisms of EFE and ACCO.
• To propose a novel reaction mechanism for ACCO based on mechanistic studies of EFE and known ACCO pathways.

Main Methods:

• Literature review of experimental and computational studies on EFE.
• Analysis of published mechanistic studies on ACCO.
• Comparative analysis of sequence and structural data for EFE and ACCO.

Main Results:

• EFE catalyzes two distinct reactions involving 2-oxoglutarate (2OG) and l-arginine.
• ACCO converts 1-aminocyclopropane-1-carboxylic acid (ACC) to ethylene, a key plant hormone.
• Both EFE and ACCO are structurally related, share sequence homology, and require Fe(II) for activity.

Conclusions:

• Understanding EFE's dual catalytic mechanisms provides insights into related enzymes.
• A novel reaction mechanism for ACCO is proposed, highlighting similarities with EFE.
• This comparative approach enhances our understanding of ethylene biosynthesis across different biological systems.