Enzyme and kinetics of enzymes
Enzymes are important components in life. The process of metabolism in
the body of the organism cannot be separated from the role of the enzyme.
For example, every food is made from carbohydrate requires
Solving both physically and chemically in the digestive process. Chemical
solutions involve an enzyme role, for example in this case carbohydrates,
will require amylase enzymes at the beginning of solutions. All cellular
activities involve enzymes. Molecular biology studies are inseparable
from enzymes.
The enzyme is a biocalamator. Almost all enzymes are protein. Enzymes
work by accelerating chemical reactions in the body by reducing
activation energy and does not change the equilibrium of the reaction. All
chemical reactions in the biology system have an energy barrier that
prevents spontaneous reactions. So that the input of energy is needed to
start the reaction.
The chemical reaction that occurs in living organisms also requires activation
energy. In biological systems, enzymes are an important component that
increases chemical reactions by reducing activation energy and helps reactions
to the level that is in accordance with cell need. Enzymes join the substrate in
such a way as to reduce the amount of energy needed for a reaction. The
mechanism of the enzyme action is explained through the Michaelis-Menten
equation. Enzyme (E) works on the substrate (s) that will form an enzyme
complex (ice), then the product will generate (p). Enzymes also work
specifically. Enzymes only work on the appropriate substrate. Different
substrates are catalyzed by different enzymes.
Perspective of enzymes
Perspective
The enzyme work on the substrate has a perspective of bonding. That is, specific
enzymes for substrates that have similar bonds and structures, for example
specific to the type of peptide bond, glycosidic bond. For example,
α
-amylase
enzymes hydrolyzing
α
-1.4 glycosidik in starch. Another example, the lipase
enzyme hydrolyzes ester bonds between glycerol and fatty acids.
Optical perspective
Specific enzymes for optical configuration. For example, amino acid oxidase-l
only works on amino acid L (Figure 4), while amino acid oxidase is only working
on Sam Amino D. Likewise in amylase enzymes, starch and glycogen
α
-
glycosidic is only hydrolyzed by
α
-glycosidase (
α
-amylase). The bonding of
β
-
glycosidics of cellulose is only hydrolyzed by
β
-glycosidase (
β
-amylase).
Clusterability
Specific enzymes for bonds and groups that surround bonds. For example, the
enzyme peptide peptide bonds where amino groups are contributed by aromatic
amino acids such as phenylalanine, tyrosine, and tryptophan. Trypsin enzymes
dismiss the peptide bonds yag donated by any alkalic amino group, such as
arginine, lysine, and histidine.
Substrate perspective
Enzyme work is also specific to one substrate and one reaction. For example,
the lactase enzyme only hydrolyzes the bond of
β
-1.4 glycosidic lactose to
produce galactose and glucose.
Geometry perspective
Single enzymes can work on different substrates that have similar molecular
geometry, so the specificity is very lacking. For example, the alcohol
dehydrogenase enzyme can oxidize ethanol and methanol to produce
appropriate alcohide because the two alcohol has similar molecular geometry.
Cofactor's perspective
Enzymes have specific cofactors. The cofactor is a non-protein part of the
enzyme. Only the right combination of enzymes and cofactors that allow an
enzymatic reaction.
Enim's nomenclature and classification
Enzymes generally have two names, common names with endings which are
traditional naming and systematic names. The common name of the enzyme
with the suffix -ase describes the substrate and the type of reaction that is
catalyzed, for example the protease enzyme hydrolyzing protein, the
dehydrogenase enzyme removes hydrogen atoms. If needed, the use of
alphanumeric is added to identify several forms of enzymes, for example RNA
Polymerase III enzymes.
The name of this common enzyme is still often used because it is shorter.
Because more and more types of new enzymes are found, the classy classy
enzyme classifieds have been agreed upon internationally. This enzyme
nomenclature system makes each enzyme have a unique name and code
number that identifies the type of reaction that is catalyzed and the substrate
involved. Systematic naming classifies enzymes to 6 classes, based on the type
of reaction that is catalyzed with each subclass. Enzyme naming agreed
according to the IUB System (International Union of Biochemistry).
Classification of six enzymes and reaction types
NUM.Enzyme Type The reaction is catalyzed Example
1 Oksidoreduktase Oxidation Reaction Alcohol
dehydrogen ase
2 Transferase Transfer C- function groups, N-. P-
Hydroxymet Yil
transferase
3 Hydrolase Hydrolysis reaction Trypsin,
urease
4. Liase The addition of Pyruvate
Each enzyme is grouped into the classroom is given a systematic name. This
systematic name induces a catalyzed reaction. For example, the enzyme that
catalyzes the reaction below:
ATP + D-glucose ADP + D-glucose -6-phosphate
The name of this enzyme system is phosphotransferase-ATP: glucose. Illustrate
that this enzyme catalyzes phosphate transfer from ATP to glucose. This enzyme
is in class 2 on table 1 above. This enzyme classification number is 2.7.1.1. The
first number is (2) is the class name (transferase). Second number (7) is a sub-
class (phosphotransferase). The third number (1) for sub-class
(phosphotransferase with a hydroxyl group as a recipient). The fourth number
(1) is for D-glucose as a recipient of the phosphate group. The usual name of this
enzyme is hexokinase.
Enzyme
The enzyme component consists of (1) apoenzyme, is a part of the active
enzyme consisting of labile proteins on environmental factors; (2) cofactors, are
components not proteins in the form of:
a) inorganic ions (Activator) are metals that binds weak with enzymes, such as
FE, CA, MN, ZN, K, CO;
b) prosthetic groups are organic compounds that bind strong with enzymes, for
example: FAD (Flavin Adenin Dinucleotide), Biotin, and Heme;
c) Coenzyme, is a non-protein non-protein molecule, which features in moving
chemical, atoms, or electrons from one enzyme to other enzymes. Example of
NAD, coenzymim-a, vitamin. Enzymes that are bound to cofactors are called
Holoenzim (complete enzymes)
Enzyme Work Mechanism
In general, the mechanism of the enzyme work occurs through the formation of
complex enzymes-substrates, then the product is formed and the enzyme
becomes free, then react again with the substrate. The enzyme section itself has
a catalytic side / active side, namely the binding place of the substrate. The three
-dimensional catalytic side, in the form of curvature on the surface of the
substrate enzyme protein binds to the active side of an enzyme through several
forms of weak chemical bonds. There are two the theories of the mechanism of
enzyme work, lock and key (lock locks) and induced fit (induction match).
Lock and Key theory
Based on the theory of lock and key, the reaction between the substrate and
enzymes is caused by the suitability of the form of space between the substrate
with the activate site. In this case, the active side of the rigid enzyme.
Induction's compatibility theory
Based on induction match theory, the reaction between enzymes and substrates
occur due to substrate induction against the active side of the enzyme. Both are
complementary structures. In this case, the active side of the enzyme is more
flexible. The theory of the mechanism of induction compatible enzymes.
Factors that affect enzyme work
pH
Enzyme work is strongly influenced by pH.
Extreme pH, very high or very low, will cross the loss enzyme activity.
Enzymes can experience denaturation so that enzymes and substrates can
change electrical charges as a result of changes in enzyme activity.
Each enzyme has its own optimum pH. For most enzymes in the body will
show optimum activity between pH 5.0-9.0.
Temperature
At low temperatures approaching frozen generally Enim is not damaged.
At temperatures when enzymes are still active, the increase in
temperature is 10 ° C, causing enzyme activity to 2 times greater (Q10 = 2).
At optimum temperature the reaction will take place the fastest.
If the temperature is increased continuously, the number of active
enzymes will decrease because it is caused by denaturation. The enzyme
in the human body has an optimum temperature of around 37 ° C.
Enzyme concentration
The speed of the enzyme reaction (V) is directly proportional to the
concentration of enzyme (ENZ).
If the enzyme concentration is getting higher, the reaction is getting fast
too.
If the substrate concentration remains, then the addition of the enzyme
concentration will not accelerate the reaction because the substrate is
saturated with the enzyme.
Substrate concentration
If the substrate concentration (s) increases, while other conditions remain
the same, then the reaction speed will also increase until a maximum V.
At the maximum point, the enzyme is saturated with the substrate. At
point A and B shows not all enzymes react with the substrate, so that at A
and B additions Subrates s resulted in the number of increasing ENZS, the
reaction speed of V increases, according to the addition of S.
At point C shows all enzymes have reacted with the substrate, the addition
of S will not increase the speed of the reaction, because there is no more
free enzyme.
At point B speed reaction exactly half the maximum speed. The substrate
considation that produces half the maximum speed is called KM price
(Michaelis Contanta).
Inhibitors
Inhibitors are substances that can inhibit enzyme activity. Inhibition of
enzymes is a process where the reaction of enzymes and subsrates stops.
Overall there are two types of inhibitors namely reversible inhibitors and
irreversible inhibitors.
Reversible Inhibor Motor can return to its original. There are four types of
reversible inhibitors,
Competitive inhibitors
Competitive inhibitors bind on the active side of the enzyme. This
inhibitor can only bind to free enzymes.
This inhibitor also sees the active side with the substrate, thereby
reducing the number of enzymes that will join the substrate.
This inhibitor does not disturb the speed of complex ice solutions to
products and can be overcome by adding substrates.
Uncompletitive inhibitors
Uncompetitive inhibitors bind complex substrates, cannot bind free
enzymes.
This inhibitor has a complex solution speed of the substrate into a product.
If there is an additional substrate to enhance inhibition.
Noncompletitive inhibitors
Non-competitive inhibitors bind the other side other than the active side.
This inhibitor can bind both complex substrates and free enzymes.
Mixed inhibitors
Mixed inhibitors are a combination of various inhibitions above.
Iireversible inhibitors bind the enzyme permanently so that the substrate
binds to the enzyme.
Alosteric obstacles
Alosteric obstacles are obstacles that occur in alosteric enzymes. Alosteric
enzymes are enzymes that have other sides besides active sisis, namely
alosteric side.
Inhibitors that inhibit alosteric enzymes are called alosteric inhibitors.
The formation of bonds between alosteric enzymes and alostionic
inhibitors will affect the enzyme, so that the active part changes in shape,
causing the incorporation of the substrate on the active side of the
enzyme to be hampered.
Enzyme kinetics
Enzyme kinetics are defined enzymes in catalyzing a reaction. Includes
how well the enzyme recognizes different SUSCRAT, how the activity is
influenced by other compounds.
Mathematical equations are used to quantify the catalytic enzyme and its
substrate affinity, and enzyme response to inhibitors.
In a simple reaction that is catalyzed by enzymes, the reactant is called
substrate (s), the reaction results are called the product (p).
The reaction speed is described by the speed of loss of reactants or the
formation of the product against time. During the process, the reverse
reaction began to take place, there was a competition to the same speed
and equilbriach achieved.
The more enzymes, the faster the reaction is running. When the substrate
concentration is low, the enzyme will quickly change into a product.
The addition of the number of substrates continues to make enzymes
become saturated because of the number of substrates more than the
number of enzymes.
At very high subsrates concentrations, enzyme activities will decrease
because they have achieved optimum value.
The speed curve versus substrate shaped hyperbole. The sector curve
shows that the enzymes combined with the substrate forming the
substrate complex (ES), then changing the substrate (s) to the product (P).
