[Biology Class Notes] on Cysteine Pdf

Overview of Cysteine

Cysteine is an amino acid important for making protein, and other metabolic functions. It is found in beta-keratin. In nails, skin, and hair, this is the main protein. Cysteine is important in the creation of collagen. It affects skin elasticity and texture. As single AAs or in AA combinations, amino acids (AAs) are available. They also come as part of multivitamins, proteins, and food supplements. The forms include tablets, fluids, and powders. IUPAC id is 2-amino-3– (2-amino-2-carboxy-ethyl) sulfanyl-propanoic acid.

Our body uses cysteine which is an amino acid with the chemical formula HO2CCH(NH2)CH2SH, as most of the amino acids are used i.e. building blocks of proteins.

Cysteine can be generally defined as a non-essential amino acid. The ones that contain cysteine are foods that have high protein. Some major sources are dairy products, poultry products and meat. Some of the plant sources are granola, onions, red peppers, lentils etc.

N-acetyl-L-cysteine (NAC) is the form when it is ingested as a supplement. From the above chemical and then converted into glutathione which is a potent antioxidant, the amino acid in context is converted. 

The free radicals present in our bodies are fought by these antioxidants. The DNA, cell wall and cell membrane is being injured by the radicals injurious compounds. With radicals, many problems have been associated such as cancer, breaking down the mucus in the body etc. A precursor in personal-care, pharmaceutical and food industries, cysteine, mainly the L-enantiomer. 

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Sources of Cysteine

Mainly in the liver, from homocysteine issued from the transmethylation of methionine, cysteine can be endogenously synthesized. Our body cysteine is created from methionine, an essential amino acid. Some of the foods that have the amino acid are enlisted below:

Pork, duck, turkey, yogurt, ricotta, granola, chicken, oat flakes, wheat germ, lunch meat, sausage meat, cottage cheese, beef liver, somen noodles etc.

Applications of Cysteine

A precursor in the food, pharmaceutical and personal-care industries is cysteine which is  mainly the l-enantiomer. The production of flavors is one of the largest applications. The reaction of cysteine with sugars in a maillard reaction yields meat flavors are the examples. A processing aid for baking is being used with  L-Cysteine.

The few amino acids that contain sulfur is one of cysteine. To bond in a special way this allows cysteine, and maintains the structure of proteins in the body. A component of the antioxidant glutathione is cysteine. To produce taurine , another amino acid cysteine is being used.

In the development of flavors cysteine also comes into play. For instance, in the Maillard reaction, it reacts with sugars to give us meaty flavors. This nonessential amino acid as a processing aid is being used by the art of baking. Its dynamics, and biomolecular structures are explored by the use of this chemical. Other applications of Cysteine are:

1. Cigarettes also contain cysteine.

2. It is also used to treat schizophrenia.

3. It acts as an antidote for hangovers and liver damage.

4. Cysteine is being used by the Asian countries for personal care applications.

5. It controls the blood sugar levels, and are widely used by the Patients of type 2 diabetes.

6. Emphysema, cystic fibrosis and asthma have shown great response to this chemical.

Fun Facts

1. Cysteine is a semi-essential amino acid, which means that humans can make it. The codons UGU and UGC code for cysteine. As a nucleophile, the thiol side chain in cysteine often does enzyme reactions. The thiol oxidized to give the disulfide derivative cystine, which is important in many protein structures.

2. L-cysteine is a non-essential amino acid which can be synthesized in the body from L-methionine and L-serine. It is conditionally essential for preterm infants. It is an important precursor for the synthesis of proteins such as glutathione, taurine, coenzyme A, and inorganic sulfate. Some anti-inflammatory properties have been shown by L-cysteine, and are important for the protection against various toxins.

3.L-cysteine plays an important role during acetaminophen overdose. For the liver’s role in detoxification, hepatic glutathione is essential, however during acetaminophen overdose, hepatic glutathione is depleted which is life-threatening. As it helps to restore hepatic glutathione, and to prevent liver damage, The L-cysteine viaN-acetylcysteine is the antidote.

4. Rare cases of cystine renal stone formation have been reported. The side effects which are most commonly reported have been gastrointestinal such as nausea.