Fig. 1
From: Q&A: How do plants respond to ethylene and what is its importance?
The two-step ethylene biosynthesis pathway in plants. In the first committed step, which is generally the rate-limiting step, ACC is synthesized from SAM by the enzyme ACS. SAM is produced from methionine in the “Yang cycle” of methionine cycling (named after Shang Fa Yang and colleagues, who elucidated the ethylene biosynthesis pathway in the 1970s). In the second step, ACC is converted to ethylene by the enzyme ACO