The key difference between arginine and citrulline is that arginine cannot expand blood vessels to a considerable extent, whereas citrulline can expand blood vessels to a comparatively greater extent.
Arginine and citrulline are two important organic compounds. These are commonly found in their L isomeric form (L-arginine and L-citrulline). The human body uses arginine for various different functions; therefore, it does not use all the arginine it absorbs for the production of NO. On the other hand, citrulline is usually highly absorbed by the gastrointestinal tract.
CONTENTS
1. Overview and Key Difference
2. What is Arginine
3. What is Citrulline
4. Arginine vs Citrulline in Tabular Form
5. Summary – Arginine vs Citrulline
What is Arginine?
Arginine or L-arginine is an important amino acid that is useful to biosynthesize proteins. It has the chemical formula C6H14N4O2 and an alpha-amino group, an alpha carboxylic group, and a side chain (having 3 carbon atoms in an aliphatic straight chain) that ends with a guanidine group. The molar mass of the compound is 174.2 g/mol. Its melting point is 260 °C, and the boiling point is 368 °C.
Figure 01: The Chemical Structure of Arginine
More importantly, it occurs as white crystals and is odorless. The sources of this amino acid include meat, dairy products, and eggs as animal sources. The plant sources are seeds of all types, such as grains, beans, and nuts. More importantly, L arginine converts into nitric oxide in the body. It causes blood vessels to open wider for improved blood flow.
What is Citrulline?
Citrulline is an organic compound having the chemical formula C6H13N3O3. It has its name derived from Citrullus, which is a Latin word for watermelon. It was named as such from the descriptions by gastroenterologists. Since the 19th century, it was isolated from watermelon (first isolated in 1914) by Japanese researchers Yotaro Koga and Ryp Odake. The IUPAC name for this compound is 2-Amino-5-(carbamoylamino)pentanoic acid.
Figure 02: The Chemical Structure of Citrulline
The molar mass of this compound is 175.18 g/mol. Citrulline appears as white crystals that are odorless. Its acidity can be described by its pKa value, which is equal to 2.508. On the other hand, the basicity can be given as pKb = 11.489.
This compound is the major intermediate in the urea cycle. The urea cycle is the pathway in mammals that is used to excrete ammonia by converting it into urea. This compound can also be produced as a byproduct of the enzymatic production of nitric oxide from the amino acid arginine. This reaction is catalyzed by nitric oxide synthase.
Furthermore, the biosynthesis of citrulline involves the production of arginine via nitric oxide synthase as a byproduct of the production of nitric oxide for signaling purposes, production from ornithine via the breakdown of proline or glutamine, and production from asymmetric dimethylarginine via DDAH.
What is the Difference Between Arginine and Citrulline?
Arginine and citrulline are two amino acid compounds important for the human body. The key difference between arginine and citrulline is that arginine cannot expand blood vessels to a considerable extent, whereas citrulline can expand blood vessels to a comparatively greater extent. Moreover, arginine is an essential amino acid, whereas citrulline is a non-essential amino acid. Arginine causes several gastrointestinal problems, while citrulline causes only a few gastrointestinal problems.
The below infographic presents the differences between arginine and citrulline in tabular form for side-by-side comparison.
Summary – Arginine vs Citrulline
Arginine and citrulline are two amino acid compounds important for the human body. The key difference between arginine and citrulline is that arginine cannot expand blood vessels to a considerable extent, whereas citrulline can expand blood vessels to a greater extent comparatively.
Reference:
1. “Citrulline.” Wikipedia. Wikipedia Foundation.
Image Courtesy:
1. “Arginine” By NEUROtiker – Own work (Public Domain) via Commons Wikimedia
2. “L-Citrulline” By NEUROtiker – Own work (Public Domain) via Commons Wikimedia