Department of Biochemistry and Integrative Medical Biology, School of Medicine, Keio University, Tokyo, Japan
Gaseous signal transduction is an event where gaseous molecules produced or utilized in the body transfer biological signals to their receptors. Molecular oxygen (O2) is not only necessary to maintain aerobic ATP synthesis in mitochondria but also serves as a primary substrate to synthesize the signaling gases, such as, nitric oxide (NO) and carbon monoxide (CO). These gaseous monoxides are generated by oxygenases, such as, NO synthase (NOS) and heme oxygenase (HO), respectively, and both play important roles in regulation of microvascular functions. Aerobic consumption of molecular oxygen occurs concurrently with glucose oxidation and thereby upregulates synthesis of CO2 in the Krebs cycle. On the other hand, 3-phosphoglyceric acid, a product of glycolysis, serves as a substrate for serine, which interacts with methionine to generate cysteine. Besides its roles in synthesis of glutathione, taurine, and sulfate ion, this amino acid serves as a substrate for cystathionine b-synthase and/or cystathionine g-lyase to generate hydrogen sulfide (H2S) (Figure 1). Among these gases, this article focused on the roles of O2, NO, and CO in microvascular signal transduction where molecular mechanisms for their reception have been revealed with physiologic implications.
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This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.