PROTEINS, AMINO ACID, ENZYMES

Amino Acids

Building block of proteins
General formula:
                            NH_z
                                      |        O
                     R - C - C                                         L form predominant
                                     OH
                                                                     COOH - acid
                                                                     R - determins the character of the amino acid

Types

A. Simple

1. Glycine                                                                     (gly)

2. Alanine                                                                     (ala)

B. Acidic - 2 acid groups

1. Aspartic acid                                                             (asp)

2. Glutamic acid                                                             (glu)

C. Basic Lysine                                                             (lys)

D. Aromatic

1. Phenylalanine                                                             (phe)

2. Tyrosine                                                                     (tyr)

3. Trytophan                                                                   (try)

E. Sulfur

Cysteine                                                            (cys)     Cystine (cys-cys)

Proteins are made up of amino acids linked together as the acid and amine groups.

Peptide linkage

Peptide means amino acids linked together in a chain.

Dipeptide - 2 amino acids aspartylphyenylanine (methyl ester is aspartamen)
Tripeptide - 3 amino acids
        Glutathione is an antioxidant γ-glutamylcystylglycine

Proteins are made up of peptide chains, which are made up of amino acids.

Sickle cell      glutamic acid       replaced valeine

Structure

Primary - order of amino acids
Secondary - Spacial arrangement
                    helix - keratin,
                    pleated
                    triple helix, collagen 30% of total protein
Tertiary - bonding & folding of chains

Quaternary - chains - subunits.

Compounds derived from amino acids

Try Serotonin Neurotransmitter. Changes in activity of serotonin neurons related to actions of psychedelic drugs.

Tyr Thyroxin Catechol Epinephrine Norepinephrine Dopamine

Epinephrine is adrenalin. Dopamine 20% normal level in Parkinson's

Phenylethylamine is a neurotransmitter gives people the feeling of Abeing in love@. Metabolite phenylacetic acid is excreted in urine. Low levels of phyenylacetic acid correlates with depression.

For the protein to function as a protein, it needs to retain its shape. A protein may be inactivated or denatured by:

(a) heat
(b) oxygen
(c) acids
(d) bases
(e) chemicals

Example of heat denaturation: cooking an egg - the clear albumin goes white.

Enzymes

Enzymes are proteins that make a reaction go - act as a catalysts.
End in ase - proteinase, methyl transferase, DNA polymerase

In liver we have detoxification enzymes which react with drugs or chemicals and then it can be excreted in the urine.

phenol

OH

+ glucuronic ---> phenyl glucuronic acid (a product of glucose)

Our whole system is enzymes. For sucrose to go to actate and yield energy, better than 20 enzymes are needed.

Some genetic defects are due to a missing enzyme.
        Albinism - loss of one of the amino acid metabolising enzymes
        PKU - loss of an enzyme which reacts with phenylalanine

Characteristics of Enzyme Activity

1. Dependent of temperature
Cooling slows down the activity

2. Dependent on pH
Each enzyme has a pH value where it works best

3. Dependent on concentration
The more present, and if substrate is available, the greater the
activity. Substrate is the compound the enzyme works on and then gives
a product.

S + E -----> SE -----> E + P

4. Co-factors - some need metals or vitamins to work.

Proteins
Functions

1. Catalysis - enzymer
2. Transport - lipoproteins, hemoglobin
3. Action - actin
4. Support - collagen
5. Protection - antibodies
6. Chemical Messengers - hormones - throxin
7. Transmission of nerve impulses - Rhodopsin
8. Storage
9. Toxin
10. Gene regulation

Draw Tyr-Gly-Gly-Phe-Leu

Enkephalin - endomorphins - tolerance to pain

receptor                                                                             Morphine ties up the sites on brain. Body
site                                                                                     stops production of endomorphins - Withdrawal
                                                                                                                Painful.

Column Chromatography         1 - size         2 - charge

Electrophoresis - charge - isoelectric point

Coenzymes

Niacin - Nicotinamide adenine dinucleotide NAD
Riboflavin - Flavin adenine dinudeotide FAD
Pantothenic Acid - Co enzyme A
Thiamine,     Pyridoxine,     Biotin,         Folic Acid         B₁₂
Metals - Copper, Zinc, iron
Zymogens - inactive form of enzyme         Chymotrypsinogen cleaves off a small 
section to make the active form of the enzyme - chymotrypsin

Makes the protein active

Inhibitors

1. Competitive Inhibition - looks a lot like the subtrate to interact with the
enzyme - ties up EZ

E + S ----> ES ----> E + I
E + I ----> EI --/-->

p-aminobenzoic acid             sulfanilamide

2. Noncompetitive - destroys a site - breaks an S-S bond. Metals will precipitate proteins

3. Feedback also called allosteric enzymes

A ----> ----> ----> ----> ----> ----> choleterol

Diagnostic Use of Enzymes

Heart attack - CPK             creatine phosphokinase
Liver damage SGOT           serum glutamic-oxaloacetic transaminase
                                          LDH   Lactate Dehydrogenase
Damaged heart muscles pours enzymes into the blood

Nitrogen Balance - BUN Blood urea nitrogen O
        nitrogen of amino acids generally appears as urea H₂N-C-NH₂
                                                + positive nitrogen balance    BUN low
                                    - negative nitrogen balance    BUN high      breakdown of Protein

Glucose In paper strip glucose oxidase imbedded

                glucose ------> glucuronic acid

Acid phosphatase - cancer of prostate

Amylase - pancreatic disease

Wednesday, March 21, 2007 01:28:02 PM