Amino acids, often referred to as the building blocks of proteins, are compounds that play many critical roles in your body. They're needed for vital processes like the building of proteins and synthesis of hormones and neurotransmitters. Some may also be taken in supplement form for a natural way to boost athletic performance or improve mood. This article tells you everything you need to know about essential amino acids, including how they function, possible food sources and the benefits of taking a supplement.
They not only serve as the building blocks for proteins but also as starting points for the synthesis of many important cellular molecules including vitamins and nucleotides.
In most cases bacteria would rather use amino acids in their environment than make them from scratch. It takes a considerable amount of energy to make the enzymes for the pathway as well as the energy required to drive some of the reactions of amino acid biosynthesis.
The genes that code for amino acid synthesis enzymes and the enzymes themselves are under tight control and are only turned on when they are needed. The amino acids synthesis pathways can be grouped into several logical units. These units reflect either common mechanisms or the use of common enzymes that synthesize more than one amino acid.
Notice that each pathway begins with a central metabolite or something derived from "central metabolism". Using common compounds instead of synthesizing them from scratch saves energy and conserves genes since fewer enzymes are needed to code for the pathways.
Simple Reactions glutamine, glutamate, aspartate, asparagine and alanine In most cases these amino acids can be synthesize by one step reactions from central metabolites.
They are simple in structure and their synthesis is also straight forward. Glutamate can by synthesized by the addition of ammonia to a-ketoglutarate.
Figure 1 - The synthesis of glutamate. Glutamine is made by the addition of another ammonia molecule to glutamate. Figure 2 - Synthesis of glutamine The rest of the simple reactions involve transfer of the amino group transamination from glutamate or glutamine to a central metabolite to make the required amino acid.
Aspartate is synthesize by the transfer of a ammonia group from glutamate to oxaloacetate. Figure 3 - The synthesis of aspartate. Asparagine is made either by transamination from glutamine or by adding ammonia directly to aspartate.
This releases more energy which is needed to drive the synthesis. Alanine synthesisis is a bit of a mystery. Several reactions have been identified, but it has been impossible to generate an alanine auxotroph and therefore positively identify a required pathway.
There are several pathways and the most likely is formation of alanine by transamination from glutamate onto pyruvate. A transamination using valine instead of glutamate is also possible. This is phosphorylated to homoserine phosphate by ATP and finally converted into threonine. Figure 6 - Synthesis of Threonine and Lysine.
Note the amount of energy that is expended in these biosytheses. The synthesis of lysine has been found to consist of different reactions in different bacterial species.
A somewhat generalize pathway is presented. Lysine synthesis involves the addition of pyruvate to aspartate semialdehyde, the use of a CoA intermediate either acetyl CoA or succinyl-CoA and the addition of an amino group from glutamate.
The group added from CoA either succinyl or acetyl serves as a blocking group, protecting the amino group from attack during transamination by glutamate.
Synthesis of serine and glycine starts with oxidation of 3-phosphoglycerate forming 3-phosphohydroxy pyruvate and NADH. A transamination reaction with glutamate forms 3-phosphoserine and removal of the phosphate yields serine.
Glycine is generated by removal of the methyl group from serine. Energy is not required for this pathway, in fact it yields energy in the form of reduced NADH. Figure 7 - Synthesis of Serine and Glycine. Note that this pathway actually yields energy and carbon for other uses.
R tetrahydropholate Branch chain amino acids leucine, isoleucine and valine Examination of the isoleucine pathway versus the valine pathway demonstrates that the only difference is the substitution of an ethyl group instead of a methyl group to the a-carbon of the intermediates.
The intermediates are so similar that common enzymes catalyze four steps of each pathway. Isoleucine synthesis begins with threonine, which is deaminated to a-ketobutyrate.
Figure 8 - Synthesis of valine and isoleucine. Leucine biosynthesis starts of with the last intermediate in the valine synthesis, a-ketoisovalerate. In the first step Acetyl-CoA is used to add an acetyl group to the molecule.
In the final step, the amine from glutamate is added to a-ketoisocaproate to form leucine.Synthesis of Nonessential Amino Acids Ignoring tyrosine (as it's immediate precursor is phenylalanine, an essential amino acid), all of the nonessential amino acids (and we will include arginine here) are synthesized from intermediates of major metabolic pathways.
The role of tRNA in protein synthesis is to bond with amino acids and transfer them to the ribosomes, where proteins are assembled according to the genetic code carried by mRNA. translation The process in which the genetic code carried by mRNA is translated into a sequence of amino acids. The amino acids synthesis pathways can be grouped into several logical units.
These units reflect either common mechanisms or the use of common enzymes that synthesize more than one amino acid. These categories are: simple reactions, branch chain amino acids, aromatic amino acids, threonine/lysine, serine/glycine, and unique pathways.
Amino Acids • Most bacteria and plants (not mammals) synthesize all 20 common amino acids • Nonessential amino acids for mammals are usually derived from intermediates of glycolysis or the citric acid cycle • Amino acids with the largest energy Amino Acid Biosynthesis.
Apr 14, · The synthesis of 4-amino-N-benzyloxycarbonyl-l-cis-proline, (5) has been previously reported. 13 Since peptide assembly using the Fmoc-strategy was envisaged, the Boc group was used to protect the primary amino group of 5.
In humans, BCAAs account for 35% of the essential amino acids found in muscle proteins. They account for 40% of the total amino acids required by your body (28).