Oxygen is an essential gasotransmitter

In biochemistry textbooks, amino acids that are derived from environment and that cannot be synthesized by cells are classified as essential amino acids. However, the gasotransmitter field is currently not considering oxygen (O2) as a gasotransmitter. This is due to one of the current criteria for a gasotransmitter, which states that 'It is endogenously and enzymatically generated, and its production is regulated’. Such a restrictive criteria has not been applied for amino acids. For me, this is equivalent to not considering essential amino acids as amino acids at all. And such a limitation will hinder the challenge, proof, disproof, or study of the theory of gasocrine signaling that I have recently proposed. I propose that for aerobic organisms, O2 derived from their environment is an essential gasotransmitter. Likewise, for any organisms whose existence is dependent on a gasotransmitters that they do not synthesize, such gasotransmitters must be considered as essential gasotransmitters for those organisms. I propose that the criteria for gasotransmitters must be relaxed to include O2 and other gasotransmitters as essential gasotransmitters. This will also enable the search for receptors for O2, similar to the research that identified soluble guanylate cyclase as a receptor for the mammalian non-essential gasotransmitter such as nitric oxide (NO). I also propose using the term 'gasoreceptor' for receptors whose structures can be altered upon the interaction with gasotransmitter and/or its derivatives, resulting in downstream cellular signaling events. An example of such gasotransmitter-gasoreceptor interaction is the reported nitric oxide/cysteine interaction or the repositioning of β H-NOX protein domain, which can regulate soluble guanylate cyclase activity. In mammals, gasoreceptors for O2 are likely expressed in nearly every cell that is exposed to O2 or its derivatives (reactive oxygen species), rather than being restricted to specialized tissues such as carotid bodies. Accepting O2 as an essential gasotransmitter will require revisions in biology text books.