Amino acids play important role for all living organisms, especially human beings. Almost all of the critical and important functions of human body have some or the other role 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, they have important job to do in other vital human functions, like digestion, signaling via neurotransmitters, and much more.
The total 20 Amino acids are divided into two important types on the basis of 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 them 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, and is encoded by the codon’s AAA and AAG. Similarly, to all other amino acids, the α-carbon is chiral and Lysine may refer to either enantiomer or a racemic mixture of both. However, the focus is usually on the active enantiomer L-Lysine.
As suggested by essential amino acids, Lysinecannot be synthesized by human body. However,it is essential for humans and hence must be obtained from the diet or dietary supplements.
Though some organisms do synthesise Lysine, and when they do, Lysine has two main biosynthetic pathways, the diaminopimelate and α-aminoadipate pathways, which appointssharp 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 that are a sub group of the nine essential amino acids. Leucine too is extremely useful in protein synthesis. Leucine is an α-amino acid,containing an α-amino group in protonated −NH3+ form, andan α-carboxylic acid group in the deprotonated −COO− form, with a side chain isobutyl group. It is a non-polar aliphatic amino acid and is encoded by the codons UUA, UUG, CUU, CUC, CUA, and CUG.
Again, as a part of essential amino acids, they are not produced within human body, and need to be consumed through diet or BCAA supplements available in market.
What Are the Common Factors Between Leucineand Lysine?
Lineal Connection Between Leucine and Lysine
The connection between the two is dated back to the early days. The ancestral organisms started synthesizingLysine, Leucine using a pathway consisting of a smaller number of enzymes equipped with a broad substrate peculiarity thatpermitted a visibleintermingling of different metabolic routes.
The first three steps of the biosynthetic pathways of Leucine route (performed by leua, leucd, and leub) and the first two of Lysine (DAP) route (performed by Ask and Asd) are stronglyconserved 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 are the outcome of 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 interlinkedLysine andLeucine.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.
Leucineand Lysine Are Both Strictly Ketogenic
When you compare both Leucine and Lysine, they both are strictly ketonic, and among all the amino acids only they can make ketone bodies, but not glucose. Which is why they are not glucogenic.
Themaking of and the breaking of biochemicals in your body is called as metabolism. The making process is known as anabolism and the breaking down refers 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, which is in contrast to the glucogenic amino acids, which are converted into glucose.
Ketogenic amino acids are unable to 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.Which is why they have important roles in the human body, leading to the study of ketogenic amino acid rich diets as possible treatment for non-alcoholic fatty liver disease and diabetes.
Lysineand Leucine in the Lys-Leu form can be utilized more efficiently for feed utilization than those in free amino acid from. 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 expression.
As we have seen, right from their classification as essential amino acids to their chemical structure to the way they are encoded, to the metabolic biological pathways they work through, and their equal and important role in protein synthesis, we saw many similarities and common factors between Leucine and Lysine. Even they both belonging to the same ketogenic group also, have a huge influence on their functioning and thus it reflects on the human functions they get involved into.