leucine and lysine

What are the Common Factors Between Leucine and Lysine? 

Amino acids play an important role for all living organisms, especially human beings. Almost all of the critical functions of the human body have some or the other part of amino acids in it.

There are about 20 amino acids that are genetically coded, and we will be having a brief look at two of them, namely, Leucine and Lysine.

What Are Amino Acids?

Amino acids are the building blocks of proteins and are present in the form of proteins in every cell, as amino acids make up proteins, and these proteins further form the cells.

Amino acids not only have a role to play in protein production or synthesis but also have an important job to do in other vital human functions, like digestion, signaling via neurotransmitters, and much more.

Amino Acids

The total of 20 Amino acids is divided into two important types based on their source. 9 Essential amino acids and 11 non-essential amino acids.

Further, Essential amino acids are subdivided into 3 Branched-chain amino acids(BCAAs), and the remaining 6 you can call non-branched chain amino acids.

So, here in this article, we will be discussing the common features between one of the three BCAAs, Leucine, and one of the non-branched chain EAAs, Lysine.

What Is Lysine?

Lysine is an α-amino acid that is useful in the process of protein synthesis. The structure of Lysine includes an α-amino group in protonated form −NH3+ form, an α-carboxylic acid group in the deprotonated form −COO−, and a side chain lysyl.

It is a basic, charged, aliphatic amino acid encoded by the codon’s AAA and AAG.

Like all other amino acids, the α-carbon is chiral, and Lysine may refer to either enantiomer or a racemic mixture. However, the focus is usually on the active enantiomer L-Lysine.

As suggested by essential amino acids, Lysinecannot is synthesized by the human body.

However, it is essential for humans and must be obtained from the diet or dietary supplements.

Though some organisms synthesize Lysine, and when they do, Lysine has two main biosynthetic pathways, the diaminopimelate, and α-aminoadipate pathways, which appoints sharp enzymes and substrates and are found in various organisms.

Catabolism of Lysineoccurs through one of the several pathways, the most common of which is the saccharopine pathway.

What Is Leucine?

Leucine is one of the 3 Branched-chain amino acids, a subgroup of the nine essential amino acids.

Leucine is extremely useful in protein synthesis. Leucine is an α-amino acid, containing an α-amino group in protonated −NH3+ form and an α-carboxylic acid group in the deprotonated −COO− form, with a side chain isobutyl group.

It is a non-polar aliphatic amino acid encoded by the codons UUA, UUG, CUU, CUC, CUA, and CUG.

Again, as a part of essential amino acids, they are not produced within the human body and need to be consumed through diet or BCAA supplements available on the market.

Common Factors Between Leucineand Lysine? 

Lineal Connection Between Leucine and Lysine

The connection between the two dates back to the early days. The ancestral organisms started synthesizingLysine, and Leucine using a pathway consisting of a smaller number of enzymes equipped with a broad substrate peculiarity that permitted a visibleintermingling of different metabolic routes.

The first three steps of the biosynthetic pathways of the Leucine route (performed by lead, lead, and lead) and the first two of the Lysine (DAP) route (performed by Ask and Asd) are strongly conserved among the organisms.

Therefore, they share a particular degree of sequence similarity with some of those involved in the AAA Lysine biosynthesis. All of them result from one or more duplication events of an ancestral set of genes.

Though considered just hypothetically, these ancestral genes might have encoded enzymes possessing broad substrate specificity and have been involved in different metabolic pathways.

This metabolic pathway inter-linked Lysine and Leucine. The first three steps of this ancestral biosynthetic pathway may have included the reactions that, in the extant organisms, are separately achieved by the enzymes of Leucine and Lysine-AAA pathways.

Leucine and Lysine Are Both Strictly Ketogenic

When you compare Leucine and Lysine, they are both strictly ketonic, and among all the amino acids, only they can make ketone bodies, but not glucose, which is why they are not glucogenic.

The making and breaking of biochemicals in your body are called metabolism. The making process is known as anabolism, and the breaking down refers to catabolism.

As we know that metabolic pathways are interlinked. Hence not all metabolic pathways connect up like the glucogenic vs. ketogenic amino acids.

A ketogenic amino acid is an amino acid that can be degraded directly into acetyl-CoA. This is the precursor of ketone bodies, in contrast to the glucogenic amino acids, which are converted into glucose.

Ketogenic amino acids cannot be converted to glucose as both carbon atoms in the ketone body are gradually degraded to carbon dioxide in the citric acid cycle.

Both the amino acids – Leucine and Lysine – are exclusively ketogenic. They have important roles in the human body, leading to the study of ketogenic amino acid-rich diets as a possible treatment for non-alcoholic fatty liver disease and diabetes.

Lysine and Leucine in the Lys-Leu form can be utilized more efficiently for feed utilization than those in free amino acid form.

In addition, compared to free amino acids, dipeptides and fish protein hydrolysate in diets may down-regulate the expression of amino acid transporters but may not affect the presentation.


As we have seen, right from their classification as essential amino acids to their chemical structure to the way they are encoded, the biological metabolic pathways they work through, and their equal and important role in protein synthesis, we saw many similarities and commonalities factors between Leucine and Lysine.

Even though they both belong to the same ketogenic group, they also have a huge influence on their functioning, and thus it reflects on the human functions they get involved in.

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