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Amino Acids & Proteins

Amino Acids & Proteins. Ghollam-Reza Moshtaghi-Kashanian Biochemistry Department Medical School Kerman University of Medical sciences. Introduction. Most biologically important macromolecules are polymers, called biopolymers. Biopolymers fall into three classes:

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Amino Acids & Proteins

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  1. Amino Acids &Proteins Ghollam-Reza Moshtaghi-Kashanian Biochemistry Department Medical School Kerman University of Medical sciences

  2. Introduction • Most biologically important macromolecules are polymers, called biopolymers. • Biopolymers fall into three classes: • polysaccharides (carbohydrates), • proteins, • nucleic acids.

  3. Proteins Amino Acids Proteins are large molecules present in all cells. They are made up of -amino acids. There are two forms of an amino acid: one that is neutral (with -NH2 and -COOH groups) and one that is zwitterionic (with -NH3+ and -COO- groups). A zwitterion has both positive and negative charge in one molecule. There are about 20 amino acids found in most proteins.

  4. Structure and Properties of Amino-acids, Protein Primary Structure • -Proteins are polymers made out by the condensation of amino-acids • -strings of amino-acids are called polypeptide chains. • -There are 20 different chemical kinds of natural amino-acids plus some • special variants. • -Each protein has a specific sequence of amino-acids (primary structure), which is determined by the DNA sequence of the gene encoding for the protein.

  5. Structure and Properties of Amino-acids, Protein Primary Structure • -Proteins with the same function from different organisms have similar primary structures • -Amino-acid sequence determines the 3-D structure in which the protein folds and its biological function. • -Proteins can have very different sizes (from 30 to ~ 100,000 residues) • -The basic module in primary sequence is the protein domain

  6. Structure and Properties of Amino-acids, Protein Primary Structure • -some proteins are monodomain others are multidomain in one chain • -some proteins are composed by more than one polypeptide chain • -Proteins can be characterized spectroscopically • -Proteins can be isolated and purified based on their differential chemical and physical properties

  7. Amino Acids

  8. Fundamentals • While their name implies that amino acids are compounds that contain an —NH2 group and a —CO2H group, these groups are actually present as —NH3+ and —CO2– respectively. • They are classified as a, b, g, etc. amino acids according the carbon that bears the nitrogen.

  9. + NH3 – CO2 + – H3NCH2CH2CO2 + – H3NCH2CH2CH2CO2 Amino Acids an a-amino acid that is anintermediate in the biosynthesisof ethylene a a b-amino acid that is one ofthe structural units present incoenzyme A b a g-amino acid involved inthe transmission of nerveimpulses g

  10. The 20 (22) Key Amino Acids • More than 700 amino acids occur naturally, but 20 (22?)of them are especially important. • These 22 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.

  11. O H + – H3N O C C R Amino Acids • 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.

  12. O H + – H3N O C C H Amino Acids • 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. Glycine (Gly or G)

  13. Glycine (Gly or G)

  14. Amino Acids O H + – H3N O C C CH3 Alanine (Ala or A)

  15. Alanine (Ala or A)

  16. Amino Acids O H + – H3N O C C CH(CH3)2 Valine (Val or V)

  17. Valine (Val or V)

  18. Amino Acids O H + – H3N O C C CH2CH(CH3)2 Leucine (Leu or L)

  19. Leucine (Leu or L)

  20. Amino Acids O H + – H3N O C C CH3CHCH2CH3 Isoleucine (Ile or I)

  21. Isoleucine(Ile or I)

  22. Amino Acids O H + – H3N O C C CH2OH Serine (Ser or S)

  23. Serine (Ser or S)

  24. Amino Acids O H + – H3N O C C CH3CHOH Threonine (Thr or T)

  25. Threonine(Thr or T)

  26. Amino Acids O H + – H3N O C C CH3SCH2CH2 Methionine (Met or M)

  27. Methionine (Met or M)

  28. Amino Acids O H + – H3N O C C CH2SH Cysteine (Cys or C)

  29. Cysteine (Cys or C)

  30. O H + – H3N O C C – OCCH2 O Amino Acids Aspartic Acid (Asp or D)

  31. Aspartic Acid (Asp or D)

  32. O H + – H3N O C C H2NCCH2 O Amino Acids Asparagine (Asn or N)

  33. Asparagine (Asn or N)

  34. O H + – H3N O C C – OCCH2CH2 O Amino Acids Glutamic Acid (Glu or E)

  35. Glutamic Acid (Glu or E)

  36. O H + – H3N O C C H2NCCH2CH2 O Amino Acids Glutamine (Gln or Q)

  37. Glutamine (Gln or Q)

  38. Amino Acids O H + – H3N O C C CH2CH2CH2NHCNH2 + NH2 Arginine (Arg or R)

  39. Arginine (Arg or R)

  40. Amino Acids O H + – H3N O C C + CH2CH2CH2CH2NH3 Lysine (Lys or K)

  41. Lysine (Lys or K)

  42. O H + – H2N O C C CH2 H2C CH2 Amino Acids Proline (Pro or P)

  43. Proline (Pro or P)

  44. O H + – H3N O C C CH2 Amino Acids Phenylalanine (Phe or F)

  45. Phenylalanine (Phe or F)

  46. O H + – H3N O C C CH2 OH Amino Acids Tyrosine (Tyr or Y)

  47. Tyrosine (Tyr or Y)

  48. O H + – H3N O C C CH2 N H Amino Acids Tryptophan (Trp or W)

  49. Tryptophan (Trp or W)

  50. CH2 N NH Amino Acids O H + – H3N O C C Histidine (His or H)

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