Enzymes

Enzymes are proteins synthesized in the cells of living organisms in order to play the role of bio-catalysts. Catalysts are substances that accelerate chemical reactions without interfering at the reaction products. Chemical reaction is a process that converts one or more substances (known as reagents, reactants, or substrates) to another type of substance (the product). As a catalyst, an enzyme can facilitate the same chemical reaction over and over again.

Types of Enzymes
Enzymes can be classified by the kind of chemical reaction catalyzed.

o Addition or removal of water
Hydrolases
Catalyze the hydrolytic reactions (the cleavage of bonds in molecules with the help of water molecule).
Examples are:
1. Lipases, phospholipase
2. Disaccharidases (saccharase, maltase, lactase)
3. Proteases, peptidases (pepsin, trypsin)
4. Esterases
5. Phosphatases

o Transfer of electrons
Catalyze reactions involving the oxidation of one and the reduction of the other component. They often use cofactors – e.g. NAD+, NADP+, FAD or heme.
Examples are:
1. Oxidases, peroxidases.
2. Oxygenases: they bring oxygen molecule into the molecule, either as a -OH group (monooxygenases, also called hydroxylases) or as a O2 (dioxygenases).
3. Dehydrogenases: they oxidise the substrate by eliminating H-atoms; they are often abbreviated as DH (e.g. lactate dehydrogenase – LDH, alcohol dehydrogenase – ADH).
4. Desaturases.

o Transfer of a radical
Transferases participate on the transfer of various groups (amino-, acyl-, methyl-, glycosyl-, phosphoryl-,) from one molecule to another.
Examples are:
1. Transglycosidases – of monosaccharides.
2. Transphosphorylases and phosphomutases – of a phosphate group
3. Transaminases – of amino group.
4. Transmethylases – of a methyl group.
5. Transacetylases – of an acetyl group.

o Splitting or forming a C-C bond
Lyases (synthases)
Catalyze the removal of a certain group from the substrate (elimination reaction) by means other than hydrolysis (non-hydrolytic cleavage, for example of bonds between C-C or C-N). They also catalyze additions to the double bond and synthetic reactions without ATP consumptions.
Examples are:
a) Decarboxylases
b) Aldolases
c) Dehydratases, hydratases

o Changing geometry or structure of a molecule
Isomerases
Catalyse changes within one molecule of substrate (intramolecular changes), so that the product is an isomer of the substrate.
Examples are:
a) Epimerases: change the position of one –OH group in the molecule
b) Mutases: change the position of a phosphate group within the molecule

o Joining two molecules through hydrolysis of pyrophosphate bond in ATP or other tri-phosphate
Ligases (synthetases)
Catalyse synthetic reactions associated with the ATP hydrolysis (coupling of exergonic and endergonic reactions).
Examples are:
a) Carboxylases
b) DNA-ligases

Factors affecting Enzyme Activity
Several factors affect the rate at which enzymatic reactions proceed – temperature, pH, enzyme concentration, substrate concentration, and the presence of any inhibitors or activators.

Temperature
Increasing temperature, the rate of reaction will increase, because of increased Kinetic Energy. However, the effect of bond breaking will become greater and greater, and the rate of reaction will begin to decrease.

Enzyme’s Optimum Temperature
The temperature at which the maximum rate of reaction occurs. This is different for different enzymes. Most enzymes in the human body have an Optimum Temperature of around 37.0 °C.

pH
ph is a scale of how much ionic hydrogen (H+) concentration is in a substance, and therefore a good indicator of the Hydroxide Ion (OH-) concentration. The scale runs from 0 to 14. Lower pH values mean higher H+ concentrations and lower OH- concentrations. Below or above the optimum pH level, there is a risk of the enzymes disintegrating and thereby the reaction slows down.

Enzyme’s Optimum pH
At the Optimum pH, the rate of reaction is at an optimum.
Extreme changes in pH can cause enzymes to Denature and permanently lose their function, but small changes in pH above or below the optimum do not cause a permanent change to the enzyme, since the bonds can be reformed.
Enzymes in different locations have different Optimum pH values. For example, the enzyme Pepsin functions best at around pH1.5 – 1.6 and is found in the stomach, which contains Hydrochloric Acid (pH2).

Enzyme Concentration
Increasing enzyme Concentration increases the rate of reaction of an enzyme will increase up to a point, after which any increase will not affect the rate of reaction.

Substrate Concentration
Increasing Substrate Concentration increases the rate of reaction. This is because more substrate molecules will be colliding with enzyme molecules, so more product will be formed. However, after a certain concentration, any increase will have no effect on the rate of reaction, since substrate Concentration will no longer be the limiting factor. The enzymes will effectively become saturated, and will be working at their maximum possible rate.

Inhibitors
Presence of certain substances that inhibit the action of a particular enzyme. This occurs when the inhibiting substance attaches itself to the active site of the enzyme thereby preventing the substrate attachment and slows down the process.

Activators
Some of the enzymes require certain inorganic metallic cations like Mg2+, Mn2+, Zn2+, Ca2+, Co2+, Cu2+, Na+, K+ etc. for their optimum activity. Rarely, anions are also needed for enzyme activity e.g. chloride ion (CI–) for amylase.
Improving Your Health by Naturally Increasing Enzymes in Your Body
Enzymes drive biological processes necessary for your body to build raw materials, circulate nutrients, eliminate unwanted chemicals, and many other biochemical processes that go on.

Enzymes designed to help break down different foods:
Protease: Digesting protein.
Amylase: Digesting carbohydrates.
Lipase: Digesting fats.
Cellulase: Breaking down fiber.
Maltase: Converting complex sugars from grains into glucose.
Lactase: Digesting milk sugar (lactose) in dairy products.
Phytase: Helps with overall digestion, especially in producing the B. vitamins.
Sucrase: Digesting most sugars.
Amylase: To break down carbohydrates.

We need enzymes for:
1- Energy production.
2- Absorption of oxygen.
3- Fighting infections and healing wounds.
4- Reducing inflammation.
5- Getting nutrients into your cells.
6- Carrying away toxic wastes.
7- Breaking down fats in your blood, regulating cholesterol and triglyceride levels.
8- Dissolving blood clots.
9- Proper hormone regulation.
10- Slowing the aging process.