aa protein enzyme
TRANSCRIPT
-
8/2/2019 AA Protein Enzyme
1/64
Chapter 2:Biomolecules: Amino Acids and
Peptides
Genaro F. Alderite Jr.,MSERMMedical Biochemistry
-
8/2/2019 AA Protein Enzyme
2/64
At physiological pHs (7.0 -7.4), boththe carboxyl and amino groups arecharged
-
8/2/2019 AA Protein Enzyme
3/64
-
8/2/2019 AA Protein Enzyme
4/64
-
8/2/2019 AA Protein Enzyme
5/64
Phenylalaninehydroxylase
-
8/2/2019 AA Protein Enzyme
6/64
-
8/2/2019 AA Protein Enzyme
7/64
arginase
urea
-
8/2/2019 AA Protein Enzyme
8/64
-
8/2/2019 AA Protein Enzyme
9/64
-
8/2/2019 AA Protein Enzyme
10/64
-
8/2/2019 AA Protein Enzyme
11/64
Non-protein Amino Acids
-
8/2/2019 AA Protein Enzyme
12/64
Examples of ClinicalAminoacidurias
Metabolic defects: Phenylketonuria (Phe),Tyrosinemias (Phe,Tyr), Maple Syrup UrineDisease (Leu, Val, Ile), Alcaptonuria (Tyr)
Absorption/transport defects: cystinuria (Cys),Hartnup disease , Fanconis Syndrome
These diseases are generally diagnosed fromindicators in the urine or plasma.
-
8/2/2019 AA Protein Enzyme
13/64
-
8/2/2019 AA Protein Enzyme
14/64
-
8/2/2019 AA Protein Enzyme
15/64
BONDPEPTIDE
-
8/2/2019 AA Protein Enzyme
16/64
Levels of Protein Structure
-
8/2/2019 AA Protein Enzyme
17/64
General Properties of Amino Acids:
I. Physical Properties:1. White crystalline
2. Soluble in cold water, except cysteineand tyrosine.3. Most are insoluble in alcohol.4. Most are sweet like glycine, alanine,serine and proline.5. Others like leucine are tasteless;while some are bitter like arginine.
-
8/2/2019 AA Protein Enzyme
18/64
II. Chemical Properties:1. Amino acids are amphoteric.2. They form esters with alcohol.3. Amino acids can be acetylated,benzylated or methylated.4. All amino acids except prolineand hydroxyproline react withnitrous acid with the liberation of nitrogen gas.
-
8/2/2019 AA Protein Enzyme
19/64
Chapter 3:PEPTIDES AND PROTEINS
Genaro F. Alderite Jr.,MSERM
Medical Biochemistry
-
8/2/2019 AA Protein Enzyme
20/64
Biomedical importance of proteins
in The Body:1. Enzymatic catalysis - almost all biological
reactions are enzyme catalyzed . Enzymes
are known to increase the rate of abiological reaction by a factor of 10 to the6th power! There are several thousand
enzymes which have been identified todate.
-
8/2/2019 AA Protein Enzyme
21/64
2. Binding, transport and storage - small moleculesare often carried by proteins in the physiological
setting (for example, the protein hemoglobin isresponsible for the transport of oxygen totissues). Many drug molecules are partiallybound to serum albumins in the plasma.
3. Molecular switching - conformational
changes in response to pH or ligandbinding can be used to control cellularprocesses
-
8/2/2019 AA Protein Enzyme
22/64
4. Coordinated motion - muscle is mostlyprotein, and muscle contraction is mediated by
the sliding motion of two protein filaments,actin and myosin.
5. Structural support - skin and bone arestrengthened by the protein collagen
-
8/2/2019 AA Protein Enzyme
23/64
6. Immune protection - antibodies are proteinstructures that are responsible for reacting withspecific foreign substances in the body.
7.Generation and transmission of nerve impulses -some amino acids act as neurotransmitters ,which transmit electrical signals from one nervecell to another. In addition, receptors forneurotransmitters, drugs, etc. are protein in nature.
An example of this is the acetylcholine receptor ,which is a protein structure that is embedded inpostsynaptic neurons.
-
8/2/2019 AA Protein Enzyme
24/64
8.Control of growth and differentiation --proteins can be critical to thecontrol of growth,cell differentiationand expression of DNA.
-For example, repressor proteins may bind to specific segments of
DNA, preventing expression and thusthe formation of the product of thatDNA segment.
-many hormones and growth factorsthat regulate cell function, such asinsulin or thyroid stimulatinghormone are proteins.
-
8/2/2019 AA Protein Enzyme
25/64
Classification of Proteins:
1. Simple proteins- true proteins found abundantly inboth plants and animals.a. Albumins- are soluble in water and dilute
neutral solutions.- Members include serumalbumin, lactal albumin, andovalbumin.
b.Globulins- are soluble in neutral dilute salt solutionsbut not in water.- include legumin from peas,
myosinogen from muscles.
-
8/2/2019 AA Protein Enzyme
26/64
c. Glutelins- soluble in dilute acids andalkalines but insoluble in neutral
solvents. - examples are glutenin fromwheat and oryzenin from rice.
d. Prolamines- are insoluble in ordinarysolvent but soluble in 70% alcohol at aboutneutral point.
- Present in plants such asgliadin from wheat, zein from corn, andhordein from barley.
-
8/2/2019 AA Protein Enzyme
27/64
e. Histones- soluble in water, diluteacids and alkalines but not in diluteammonia.- not readily coagulated by heat- strongly basic and occur inthe tissues in the form of saltcombinations.- examples are globin fromhemoglobin, thymus histone andscobrone of mackerel.
-
8/2/2019 AA Protein Enzyme
28/64
f. Protamines- contain smaller number of amino acids.
- strongly basic and formsoluble salts with strongmineral acids.- e.g salmin from salmonsperm
g. Scleroproteins- insluble in water andneutral solvents.
- e.g keratin of theepidermal tissues, elastin fromligaments and collagen fromhides, bones and cartilages
-
8/2/2019 AA Protein Enzyme
29/64
2. Conjugated Proteins
a. Nucleoproteins- are combination of histones and protamines with nucleicacid.- soluble in dilute solutions of NaCl andcan be extracted from the tissues by theuse of this solvent.- typical examples are chromatin, andthe products obtain from glandulartissues and germ of grains.
-
8/2/2019 AA Protein Enzyme
30/64
b. Glycoproteins- are compounds of proteinswith a carbohydrate component.
- they are utilized for lubricatingpurposes in view of their slimynature.
- mucin from saliva, tendomucoidfrom tendons and osseomucoidfrom bones belong to this group.
- are not digested in the GItract and used as protection.
-
8/2/2019 AA Protein Enzyme
31/64
c. Phosphoproteins- have the prosthetic group(H 3PO 4) joined in the protein
molecule.- casein from milk and vitelline
of the egg yolk are rich in this type of
protein.
d. Chromoproteins- are protein compounds with
hematin or similar pigments in theirmolecule.- examples are hemoglobin, cytochromes
and rhodopsin.
-
8/2/2019 AA Protein Enzyme
32/64
e. Lipoproteins- have fatty substancescombined with their moleculeslike lecithin, cephalin, etc.- they are present in the blood
serum, brain tissues, cell nuclei,egg yolk and milk.
-
8/2/2019 AA Protein Enzyme
33/64
3. Derived Proteins- substances formed fromsimple and conjugated proteins.
a. Primary protein derivatives- are proteinswhich have undergone intramolecular
rearrangement through the hydrolyticaction of certain physical and chemicalagents.- They are synonymous withdenatured proteins.
1 P t i l bl b t
-
8/2/2019 AA Protein Enzyme
34/64
a1. Proteans- are insoluble substancesresulting from the preliminary action of water, dilute acids, or enzymes.- myosan from myosin and edestanfrom edestin are good examples.
a2. Metaproteans- are product of furtherhydrolysis.- soluble in weak acids andalkalies, but insoluble in neutralsalt solutions.
-acid metaproteans(acid albuminate);alkali metaproteans (alkali albuminate
-
8/2/2019 AA Protein Enzyme
35/64
a3. Coagulated proteins- are insolubleproducts resulting from either theaction of heat, alcohol, ultravioletare or even simple mechanicalshaking.-cooked egg albumin, cooked
meat,etc.
-
8/2/2019 AA Protein Enzyme
36/64
b. Secondary protein derivatives- are products of more extensive hydrolysis.
b1. Primary proteoses- are soluble in water,precipitated by concentrated nitric acid.
- not coagulated by heat.b2. Secondary proteoses- precipitated only bycomplete saturation with ammonium sulfate
but not with nitric or picric acid.
-
8/2/2019 AA Protein Enzyme
37/64
b3. Peptones- are insoluble in water, notcoagulated by hear and not precipitated by
ammonium sulfate but by certain alkaloidalreagents such as phosphotungstic and tannicacids.
b4. Peptides- are combinations of two or moreamino acids , the carboxyl group of one beingunited with the amino group of the other.
-same properties with peptones.-ex: di,tri,tetra, penta,poly
-
8/2/2019 AA Protein Enzyme
38/64
Protein Structure Levels
PRIMARY: the linear sequence ofamino acids linked together by peptide
bonds SECONDARY: regions within
polypeptide chains with regular,
recurring, localized structure stabilizedby H-bonding between constituentamino acid residues
-
8/2/2019 AA Protein Enzyme
39/64
Secondary Protein Structure: a-helix
& b-sheet
-
8/2/2019 AA Protein Enzyme
40/64
Super-secondary structure examples
-
8/2/2019 AA Protein Enzyme
41/64
TERTIARY: the overall three-dimensionalconformation of a protein
QUATERNARY: the three-dimensionalconformation of a protein composed of
multiple polypeptide subunits
THE PRIMARY AMINO ACID SEQUENCEIS THE ULTIMATE DETERMINANT OFFINAL PROTEIN STRUCTURE
-
8/2/2019 AA Protein Enzyme
42/64
Myoglobin b -subunit Hemoglobin
-
8/2/2019 AA Protein Enzyme
43/64
Structure of Myoglobin and
Hemoglobin The amino acid sequences of myoglobin and
hemoglobin are similar (or, highly conserved) but
not identical Their polypeptide chains fold in a similar manner Myoglobin is found in muscles as a monomeric
protein; hemoglobins are found in matureerythrocytes as multi-subunit tetrameric proteins.Both are localized to the cytosol
-
8/2/2019 AA Protein Enzyme
44/64
Stabilizing Forces
1. Electrostatic/ionic2. Hydrogen bonds3. Hydrophobic interactions4. Disulfide bonds
-
8/2/2019 AA Protein Enzyme
45/64
-
8/2/2019 AA Protein Enzyme
46/64
1. Electrostatic/ionic 3. Hydrophobic interactions2. Hydrogen bonds 4. Disulfide bonds
-
8/2/2019 AA Protein Enzyme
47/64
-
8/2/2019 AA Protein Enzyme
48/64
Biochemical Methods to Analyze
Proteins Electrophoresis Chromatography: Gel filtration, ion
exchange, affinity Mass Spectrometry, X-ray
Crystallography, NMR
-
8/2/2019 AA Protein Enzyme
49/64
Gel filtration
Separation is based on protein size.Dextranor polyacrylamide beads of uniform
diameter are manufactured with differentpore sizes.
Depending on the sizes of the proteins to be
separated, they will enter the pore if smallenough, or be excluded if they are too large.
-
8/2/2019 AA Protein Enzyme
50/64
-
8/2/2019 AA Protein Enzyme
51/64
Ion Exchange Chromatography
Separation of proteins based on the netcharge of their constituent amino acids.
Different salt concentrations can be used toelute the bound proteins into tubes in a
fraction collector. Resins for binding (+) or(-) charged proteins can be used
-
8/2/2019 AA Protein Enzyme
52/64
-
8/2/2019 AA Protein Enzyme
53/64
Affinity Chromatography
Based on the target proteins ability to bind aspecific ligand, only proteins that bind to
this ligand will be retained on the columnbead.
This is especially useful for immunoaffinity
purification of proteins using specificantibodies for them.
-
8/2/2019 AA Protein Enzyme
54/64
Physical and Chemical Properties of
-
8/2/2019 AA Protein Enzyme
55/64
Physical and Chemical Properties of Proteins:
1. When pure, proteins are generally tastelessexcept with hydrolates.
2. Mostly colorless.3. Insoluble in fat solvents and present varied
degrees of solubility in water, salt solution, dilute
acids and alkalies.4. Proteins are amphoteric.5. Proteins are very reactive and highly specific.
-
8/2/2019 AA Protein Enzyme
56/64
Solubility of Proteins: (Major
influences)
1. The effect of neutral salt.
2. The effect of pH.3. The effect of organic solvents.
-
8/2/2019 AA Protein Enzyme
57/64
Actions of Heat
- when burned, proteins decompose and liberatea characteristic odor of burned hair or feather.
- solutions of proteins when heated between 38-60 degrees centigrade, undergo slight
intramolecular rearrangements.( DENATURATION)
-
8/2/2019 AA Protein Enzyme
58/64
Precipitations:
1. By acids2. By salts of Heavy metals
3. By alcohol
Hydrolysis:
1. Dilute acids; alkalies or enzymes- due to addition of elements in the peptide bond/ linkage.
-
8/2/2019 AA Protein Enzyme
59/64
CLINICAL SIGNIFICANCE OF
PROTEIN:1. The substitution of a hydrophobic amino
acid (V) for an acidic amino acid (E) in the
-chain of hemoglobin results in sickle cellanemia (HbS). This change of a singleamino acid alters the structure of hemoglobin molecules in such a way that
the deoxygenated proteins polymerize andprecipitate within the erythrocyte, leading totheir characteristic sickle shape.
-
8/2/2019 AA Protein Enzyme
60/64
b. Osteogenesis imperfecta also encompasses
-
8/2/2019 AA Protein Enzyme
61/64
g p pmore than one disorder. At least four biochemicallyand clinically distinguishable maladies have beenidentified as osteogenesis imperfecta, all of whichare characterized by multiple fractures and resultantbone deformities.
c. Marfan syndrome manifests itself as adisorder of the connective tissue and was originallybelieved to be the result of abnormal collagens.However, recent evidence has shown that Marfansyndrome results from mutations in the extracellularprotein, fibrillin, which is an integral constituent of the non-collagenous microfibrils of the extracellularmatrix.
-
8/2/2019 AA Protein Enzyme
62/64
3. Several forms of familial hypercholesterolemiaare the result of genetic defects in the gene
encoding the receptor for low-densitylipoprotein (LDL). These defects result in thesynthesis of abnormal LDL receptors that are
incapable of binding to LDLs, or that bindLDLs but the receptor/LDL complexes are notproperly internalized and degraded. The
outcome is an elevation in serum cholesterollevels and increased propensity toward thedevelopment of atherosclerosis.
4 A b f t i t ib t t ll l
-
8/2/2019 AA Protein Enzyme
63/64
4. A number of proteins can contribute to cellulartransformation and carcinogenesis when their
basic structure is disrupted by mutations in theirgenes. These genes are termed proto-oncogenes.For some of these proteins, all that is required toconvert them to the oncogenic form is a singleamino acid substitution. The cellular gene, RAS, isobserved to sustain single amino acid substitutionsat positions 12 or 61 with high frequency in colon
carcinomas. Mutations in RAS are most frequentlyobserved genetic alterations in colon cancer.
-
8/2/2019 AA Protein Enzyme
64/64
MARAMINGSALAMAT!