Proteins not only catalyze all or most of the reactions in living cells, they control virtually all cellular process. In addition, proteins contain within their amino acid sequences the necessary information to determine how that protein will fold into a three dimensional structure, and the stability of the resulting structure.
The field of protein folding and stability has been a critically important area of research for years, and remains today one of the great unsolved mysteries. It is, however, being actively investigated, and progress is being made every day.
As we learn about amino acids, it is important to keep in mind that one of the more important reasons to understand amino acid structure and properties is to be able to understand protein structure and properties. Features Asparagine is found in abundance in asparagus, and is thus named so. Asparagine is not an essential amino acid, meaning that it is not necessary for humans to ingest it to receive necessary amounts.
Asparagine has a high propensity to hydrogen bond, since the amide group can accept two and donate two hydrogen bonds. It is found on the surface as well as buried within proteins. It is a common site for attachment of carbohydrates in glycoproteins. Food sources that contain asparagine is dairy, beef, poultry, and eggs. Functions Asparagine, along with glutamate, is an important neurotransmitter.
Since Aspartic acid and Asparigine have high concentration in the hippocampus and hypothalamus of the brain, which is important in short-term memory and emotions, the two amino acids serves essential role between the brain and the rest of the body. Asparagine is required by the nervous system to maintain equilibrium and is also required for amino acid transformation from one form to the other which is achieved in the liver. Synthesis Synthesis of asparagine requires oxaloacetate, C4H4O5. The double bonded oxygen attached to carbon-2 is replaced by ammonium group from glutamate via a process called transaminase.
The newly formed compound, or aspartate, is converted to asparagine by replacing a negatively charged oxygen end with an ammonium group. Analysis Asparagine can be identified by following methods: UV spectrometry, infrared spectroscopy IR , nuclear magnetic spectroscopy, NMR , and mass spectroscopy. Its molecular weight is Also known as aspartate, Aspartic acid is an acidic and polar amino acid that has carboxylic acid group, which loses a proton to be carboxylate group for physiological pH and has a negative charge; the carboxylic acid group of the amino acid has a pKa value of 4.
Its pI is 5. Proteins are critical to maintain the pH balance in the body. It is the charged amino acids that are involved in the buffering properties of proteins. This carboxylic acid group is what makes aspartate an acidic amino acid. Aspartate and oxaloacetate are interconvertable by a simple transamination reaction. Oxaloacetate is one of the intermediates of the Krebs cycle. The Krebs cycle is the sequence of reactions by which most living cells generate energy during the process of aerobic respiration.
Features Aspartic acid is a non-essential amino acid can be obtained from central metabolic systems. Functions Aspartic acids are involved in transamination in which oxaloacetate and aspartate is interconvertible. It is also involved in immune system activity by promoting immunoglobulin production and antibody production.
Moreover, aspartic acid protects the liver and helps in detoxification of ammonia. Aspartate, the conjugate base of aspartic acid, also functions as a neurotransmitter. Along with few other amino acids, its primary role is to activate NMDA receptors in brain and; however, its effect is not significant as glutamate's. Other than its role as an excitatory neurotransmitter, aspartate is proteinogenic amino acids that are used in coding of DNA.
Aspartate plays important roles as acids in enzyme active centers, as well as in maintaining the solubility and ionic character of proteins. Synthesis Aspartic acid is synthesized from oxaloacetate via transamination. Aspartic acid can be used as an initial reactant in synthesis of other essential amino acids as well: methionine, threonine, isoleucine, and lysine.
Its alternate name is 2-aminomercaptopropanoic acid. Two cysteine residues can be oxidized to form stable disulfide bonds. Disulfide bonds can help to give a protein secondary and tertiary structure, e. The unit of two bonded cysteines is known as cystine. Cysteine is considered to be a hydrophilic amino acid based on the fact that the thiol group interacts well with water.
It is also a non-essential amino acid, and can be biosynthesized in human bodies. Functions Nucleophilic thiol groups in cysteine can be easily oxidized; thus, cystein is highly reactive with its neutral pKa and has various functions in biology. Cysteine is capable of inactivation of insulin in bloodstream.
Excessive amount of cysteine reduces one of three disulfide bonds in insulin structure. As a result, insulin loses its functionality.
Cysteine's capability of inactivation of insulin can be utilized in medicine and pharmaceutic when a patient experiences hypoglymecia attack due to high level of insulin. Cysteine promotes iron production in iron deficiency anemia. It also assists in lung diseases by increasing production of red blood cells. Cysteine is a key, active site residue in many important proteins.
Cysteine is the key residue in glutathione reductases which has protective effects against UV light, radiation, and free radicals. Additionally, glyceraldehydephosphate dehydrogenase, a key enzyme in glycolysis, uses cysteine in to achieve its most critical functions. The body makes this into cysteine and then into glutathione, a powerful antioxidant.
Antioxidants fight free radicals which are harmful compounds in the body that cause damage to the cell membranes and DNA. Researchers believe the free radicals play a role in aging as well as the development of a number of health problems, including heart disease and cancer. NAC can also help prevent side effected caused by drug reactions and toxic chemicals. It also helps break down mucus in the body. COPD is the acronym for chronic obstructive pulmonary disease.
Doctors often give NAC to people who have taken an overdose of acetaminophen Tylenol. The NAC helps to prevent or reduce liver and kidney damage. NAC also helps reduce angina. Angina is chest pain or discomfort when the heart muscle does not get enough blood. Taking NAC will open the blood vessels and improve blood flow to the heart. Studies have also shown that NAC may help relieve symptoms of chronic bronchitis, leading to fewer flare ups.
Not all studied gave these results. Some studies did not find any reduction in flare ups. Another study shows that people who took NAC two times a day had fewer flu symptoms than those who took placebo. Other results did not coincide with these results.
For example, giving NAC to people with ARDS helped reduce the severity of their conditions while not reducing the number of overall deaths compared to placebo. Cysteine is important in keratin structure, which is important in hair and nails formation on skin. Wool obtained from sheeps, and other animals is cysteine containing. Biosynthesis The precursors of synthesis of cysteine are serine and methionine.
Serine has a hydroxide group and methione has a sulfer as their substituents. Methione is initially converted into a homocysteine. Finally, addition of water and departure of ammonia from cystathione result in cysteine and alpha-ketobutyrate as a side-product.
It is a polar and uncharged derivative of acidic amino acid glutamic acid or glutamate; it has a carboxamide group, which is neutral at physiological pH and can be changed to carboxylic acid by hydrolysis to form glutamate amino acid.
Glutamine Final Synthesis As previously stated, glutamine is a nonessential amino acid. In the body, glutamine is synthesized from glutamate via the enzyme glutamine synthestase GS and through the addition of ATP and ammonia.
See Figure. ATP is directly involved in the reaction because it phosphorylates the carboxyl group on the side chain of glutamate and forms an acyl-phosphate intermediate See Figure: Glutamine Final. The acyl-phoshphate intermediate reacts with free ammonia and forms glutamine. Glutamine synthetase GS plays a major role because a high-affinity binding-site for ammonia is formed in GS after the formation of the intermediate to prevent hydrolysis of the intermediate.
Hydrolysis of the intermediate would not yield glutamine and thus waste a valuable molecule of ATP. Functions Glutamine is a non-essential amino acid, which means that it will naturally occur in the human body and does not need to be gathered from exogenous sources.
It is one of the most abundant amino acid manufactures in the body. Glutamine circulates in the blood and is able to cross the blood-brain barrier directly. Glutamine has various functions in biochemistry.
Its primary role is protein synthesis, but it also helps to maintain neutral pH in the liver by balancing the acid and base levels. Like glucose, glutamine is capable of fueling cell bodies. It donates nitrogen to cells via anabolic reactions and provides carbons in the citric acid cycle. It is critical in the gastrointestinal system in that it provides energy to the small intestine. Notably, intestine is the only organ in the body that uses glutamine as a primary energy source.
The kidney, activated immune cells, and cancer cells also require glutamine, but not as a primary energy source.
Within a cell, glutamine is essential for cell growth and protein translation. Moreover, it serves as a nitrogen donor and assists in maintaining the gradient across the mitochondrial membrane. Normal cells require glutamine.
On the other hand, cancer cells use glutamine in quantities much higher than normal cells. As discussed in the paper "Glutamine addiction: a new therapeutic target in cancer" by David R. Wise and Craig B. In this addiction, cancer cells will uptake glutamine from the body in much larger amounts than is necessary for cellular function.
In fact, cancer cells will intake more glutamine than the cell can metabolize. Depriving cancer cells of this excess glutamine causes them to die. Such deprivation is the key to potential glutamine-based cancer therapy. Glutamine consumption can exceed the consumption of any other amino acid in the cell by tenfold. In cancer cells, a metabolic shift occurs so that glutamine replaces glucose as the major source of carbon for the cell. The body can make enough glutamine for its regular needs, but extreme stress, such as heavy exercise or an injury , will make the body require more glutamine.
Most glutamine is stored in muscles followed by the lungs, where much of the glutamine is made. Usually the body can make enough glutamine so it is not necessary to take supplements of glutamine. Certain medical conditions, including injuries, surgery, infections, and prolonged sites, can lower glutamine levels, however.
In these cases, taking a glutamine supplement may be helpful. Glutamine is important for removing excess ammonia, which is a common waste product in the body. Glutamine also helps your immune system function and is need for normal brain function and digestion. Glutamine is important in wound healing and recovery form an illness. When the body is stressed, it releases hormone cortisol into the bloodstream. Other studies have shown that adding glutamine to enteral nutrition it will help reduce the rate of death in trauma and critically ill people.The required biopterin is in the form of tetrahydrobiopterin often designated BH4 or H4B. A reduction in brain tyrosine levels would then result in reduced synthesis of the neurotransmitters dopamine and norepinephrine. Glutamine supplements also help in the recovery of severe burns. Biopolymers , 90 2 , When the water PII is absent, S. Notably, favorite is the only limitation in the body that tells glutamine as a primary energy Ribosome lipid synthesis inhibitor. Forestland, Patrick G. Identification and optimization of an implicit peptide from the ant subtlety toxin pilosulin. Metaformin, a biguanide class kid, inhibits this mechanism. Deng, Y.
On the other hand, cancer cells use glutamine in quantities much higher than normal cells. This represents a major link between glutamine and the sulfur necessary for biomass synthesis, particularly in rapidly dividing tumor cells. Proline and arginine are derived from glutamate. Mutations in the methionine synthase MTR gene are also associated with inherited hyperhomocysteinemia. Dustin S. This reaction is a critically important reaction of membrane lipid homeostasis.
Functions Glutamine is a non-essential amino acid, which means that it will naturally occur in the human body and does not need to be gathered from exogenous sources. In rapidly dividing cells such as small intestinal enterocytes, lymphocytes, and especially cancer cells, glutamine is rapidly consumed and used for both energy generation and as a source of carbon and nitrogen for the synthesis of biomass. However, the mutations in PCBD1 are not associated with significant pathology. Although it would be assumed that increased intake of vitamin B12 should lead to increased conversion of homocysteine to methionine and thus, reduced levels of circulating homocysteine, controlled studies have shown that this does not occur. So, in addition to inhibiting the first enzyme of the aspartate families biosynthetic pathway, lysine also inhibits the activity of the first enzyme after the branch point, i.
The initial stages leading to the binding and functioning of membrane-active polypeptides including hormones, signal sequences, and lytic peptides are mainly governed by electrostatic attraction and hydrophobic partitioning between water and lipid bilayers. The GLUD2 gene is thought to have arisen as a result of a retrotranspostitional event to the X chromosome. Homocysteine can be converted back to methionine by methionine synthase also called homocysteine methyltransferase. The adenosine is removed from SAH via the action of adenosine homocysteinase also called S-adenosylhomocysteine hydrolase generating homocysteine. The cytosolic enzyme is derived from the SHMT1 gene located on chromosome 17p The amino group transported from the muscle to the liver in the form of alanine is converted to urea in the urea cycle and excreted.
Reaction catalyzed by asparaginase Asparagine is synthesized from aspartate via an amidotransferase reaction catalyzed by asparagine synthetase. Biosynthesis The precursors of synthesis of cysteine are serine and methionine. Materials Science and Engineering: C , 75, WBS is associated with multiple organ system involvement typically showing supravalvular aortic stenosis SVAS , mental retardation, and distinctive facial features. In turn, reduced levels of SAM in the brain are a contributor to the neural degeneration i. The glutamine synthetase enzyme is encoded by the glutamate-ammonia ligase gene symbol: GLUL which is located on chromosome 1q
Additionally, during periods of fasting, skeletal muscle protein is degraded for the energy value of the amino acid carbons and alanine is a major amino acid in protein. In the direction of glutamate deamination, glutamate dehydrogenase is activated by ADP. Functions Asparagine, along with glutamate, is an important neurotransmitter. The aspartate pathway uses L-aspartic acid as the precursor for the biosynthesis of one fourth of the building block amino acids.