Amino Acids Peptides and Proteins Classification of Amino
- Slides: 41
Amino Acids, Peptides, and Proteins.
Classification of Amino Acids
Fundamentals While their name implies that amino acids are compounds that contain an —NH 2 group and a —CO 2 H group, these groups are actually present as —NH 3+ and —CO 2– respectively. They are classified as a, b, g, etc. amino acids according the carbon that bears the nitrogen.
Amino Acids + NH 3 a CO 2– + – H 3 NCH 2 CO 2 b + – H 3 NCH 2 CH 2 CO 2 g an a-amino acid that is an intermediate in the biosynthesis of ethylene a b-amino acid that is one of the structural units present in coenzyme A a g-amino acid involved in the transmission of nerve impulses
The 20 Key Amino Acids More than 700 amino acids occur naturally, but 20 of them are especially important. These 20 amino acids are the building blocks of proteins. All are a-amino acids. They differ in respect to the group attached to the a carbon. These 20 are listed in Table 1.
Table 27. 1 + H 3 N H C O C – O R The amino acids obtained by hydrolysis of proteins differ in respect to R (the side chain). The properties of the amino acid vary as the structure of R varies.
Table. 1 Glycine (Gly or G) + H 3 N H C O C – O H Glycine is the simplest amino acid. It is the only one in the table that is achiral. In all of the other amino acids in the table the a carbon is a stereogenic center.
Table. 1 + H 3 N H C O C CH 3 Alanine (Ala or A) – O
Table. 1 + H 3 N H C O C – O CH(CH 3)2 Valine (Val or V)
Table. 1 + H 3 N H C O C – O CH 2 CH(CH 3)2 Leucine (Leu or L)
Table. 1 + H 3 N H C O C – O CH 3 CHCH 2 CH 3 Isoleucine (Ile or I)
Table. 1 + H 3 N H C O C CH 3 SCH 2 Methionine (Met or M) – O
Table. 1 + H 2 N H 2 C H C C H 2 O C CH 2 Proline (Pro or P) – O
Table. 1 + H 3 N H C O C – O CH 2 Phenylalanine (Phe or F)
Table. 1 + H 3 N H C O C – O CH 2 Tryptophan N H (Trp or W)
Table. 1 + H 3 N H C O C H 2 NCCH 2 O Asparagine (Asn or N) – O
Table. 1 + H 3 N H C O C H 2 NCCH 2 O Glutamine (Gln or Q) – O
Table. 1 + H 3 N H C O C CH 2 OH Serine (Ser or S) – O
Table. 1 + H 3 N H C O C CH 3 CHOH Threonine (Thr or T) – O
Table. 1 + H 3 N H C O C – OCCH 2 O Aspartic Acid (Asp or D)
Table. 1 + H 3 N H C O C – OCCH 2 O Glutamic Acid (Glu or E)
Table. 1 + H 3 N H C O C – O CH 2 Tyrosine (Tyr or Y) OH
Table. 1 + H 3 N H C O C CH 2 SH Cysteine (Cys or C) – O
Table. 1 + H 3 N H C O C – O + CH 2 CH 2 NH 3 Lysine (Lys or K)
Table. 1 + H 3 N H C O C – O CH 2 CH 2 NHCNH 2 + NH 2 Arginine (Arg or R)
Table. 1 + H 3 N H C O C CH 2 N NH Histidine (His or H) – O
2 Stereochemistry of Amino Acids
Configuration of a-Amino Acids Glycine is achiral. All of the other amino acids in proteins have the L-configuration at their a carbon. – CO 2 + H 3 N H R
Peptides
Peptides are compounds in which an amide bond links the amino group of one a-amino acid and the carboxyl group of another. An amide bond of this type is often referred to as a peptide bond.
Alanine and Glycine H + H 3 N C CH 3 H O C – O + H 3 N C H O C – O
Alanylglycine + H 3 N H C CH 3 H O C N C H H O C – O Two a-amino acids are joined by a peptide bond in alanylglycine. It is a dipeptide.
Alanylglycine + H 3 N N-terminus H C CH 3 H O C N C H H Ala—Gly AG O C – O C-terminus
Alanylglycine and glycylalanine are constitutional isomers + H 3 N H C C CH 3 + H 3 N H C H H O N C H H H O C N C H CH 3 O C – O Alanylglycine Ala—Gly AG – O Glycylalanine Gly—Ala GA O C
Alanylglycine + H 3 N H C CH 3 H O C N C H H O C – O The peptide bond is characterized by a planar geometry.
Higher Peptides are classified according to the number of amino acids linked together. dipeptides, tripeptides, tetrapeptides, etc. Leucine enkephalin is an example of a pentapeptide.
Leucine Enkephalin Tyr—Gly—Phe—Leu YGGFL
Oxytocin 3 2 4 5 Ile—Gln—Asn Tyr 1 Cys N-terminus Cys—Pro—Leu—Gly. NH 2 S S 6 7 8 9 Oxytocin is a cyclic nonapeptide. Instead of having its amino acids linked in an extended chain, two cysteine residues are joined by an S—S bond.
Oxytocin S—S bond An S—S bond between two cysteines is often referred to as a disulfide bridge.
- Amidomalonate synthesis mechanism
- Mobile phase in affinity chromatography
- Amino acids are joined together in proteins by
- Amino acids classification
- Ketogenic amino acid
- Amino acid classification
- Quaternary structure of protein
- Ppgbqa
- Will amylase build keratin out of peptides
- Local hormones
- Precipitation of proteins by strong mineral acids
- Glucogenic vs ketogenic
- Why is lysine basic
- Difference between hydrophobic and hydrophilic amino acids
- Codon wheel
- Titration curve of alanine
- Titration curve of amino acids
- Deamination of amino acids
- The chain of amino acids forms a
- Transdeamination of amino acids
- 20 amino acid structure
- Right handed amino acids
- Carbohydrates gives
- Titration curve of amino acids
- Gluconeogenesis
- Plp mechanism transamination
- Phenylalanine titration
- Amino acids 2 chemsheets
- Properties of amino acids
- Epsilon amino
- Conjugated protein
- Diphthamide
- Non essential amino acids mnemonics
- Dehydration synthesis of amino acids
- Aromatic amino acids
- Phenol containing amino acids
- Phenol containing amino acids
- Peptide bond dehydration synthesis
- Properties of amino acids
- Biomedical importance of amino acids
- Are amino acids negatively charged
- Conditionally essential amino acids