False Statement: Deamination of histidine results in nitric oxide production

Nitric oxide (NO) is a gas that serves as an important signaling molecule in various physiological processes. It is produced by a family of enzymes called nitric oxide synthases (NOS). While there are several ways to produce NO, deamination of histidine is not one of them.

Production of Nitric Oxide:
NO is primarily produced by the enzymatic conversion of L-arginine to L-citrulline by nitric oxide synthases (NOS). There are three isoforms of NOS: neuronal NOS (nNOS or NOS1), inducible NOS (iNOS or NOS2), and endothelial NOS (eNOS or NOS3). These enzymes use various cofactors and produce NO as a byproduct.

Functions of Nitric Oxide:
1. Intracellular Signaling Molecule: NO functions as an important intracellular signaling molecule in various physiological processes. It regulates processes such as vasodilation, neurotransmission, immune response, and platelet aggregation.

2. Stimulation of Guanylyl Cyclase: NO can diffuse across cell membranes and enter target cells. Inside the cells, it binds to and activates the enzyme guanylyl cyclase, which catalyzes the conversion of guanosine triphosphate (GTP) into cyclic guanosine monophosphate (cGMP). cGMP acts as a second messenger, mediating various physiological effects of NO.

3. Production by Activated Neutrophils: Activated neutrophils, a type of white blood cell, are capable of producing NO. Upon activation, neutrophils release NO, which can have antimicrobial effects and modulate immune responses.

Deamination of Histidine:
Deamination is the removal of an amino group (-NH2) from an amino acid. Histidine is an essential amino acid that plays a role in protein synthesis and various metabolic processes. However, deamination of histidine does not result in the production of nitric oxide.

In conclusion, the false statement is that deamination of histidine results in nitric oxide production. Nitric oxide is primarily produced by the enzymatic conversion of L-arginine by nitric oxide synthases. It functions as an intracellular signaling molecule, stimulates guanylyl cyclase to produce cGMP, and can be produced by activated neutrophils.