Chapter 3: Enzymes

Enzymes

Secreted by loving cells & are complex organic chemical compounds with definite structure.

Enzymes

Like organic catalysts, it speeds ups chemical reactions without bringing affected in the process.

Enzymes can be used over and over again.

What is the distinct property of enzymes?

Enzymes

Are the largest & MOST HIGHLY SPECIALIZED class of proteins.

Metabolism

A reaction completed very rapidly by enzymes to maintain life.

1. Water-soluble

2. Globular

3. Molecular Wight (12,000-1million)

4. May consists of a single polypeptide chain or several polypeptide chains

What are some general properties of enzymes?

Enzymes are:

1. ENDOWED with catalytic power and SPECIFICITY.

   1. Specificity in the reaction catalyzed

   2. Specificity in substrates

      1. usually catalyzes a single chemical reaction;

      2. or a set of closely related reactions

2. REGULATED activity

3. ENERGY TRANSFORMATION

What are the key characteristics of enzymes?

Process:

CO2+H2O→(carbonic anhydrase)H2CO3

Explanation:

1. In the process of carbonic anhydrase the formation is increased by 108 times.

2. Can only be catalyzed by carbonic anhydrase

Explain the process and identify the characteristic of Enzyme described.

Enzymes can either be:

1. Simple: Entirely composed of amino acids

2. Conjugated: Requires non-protein (prosthetic group) group for biological activity

What are the classification of enzymes in terms of protein parts?

PTCRUM (pregnant c rum)

1. Pepsin

2. Trypsin

3. Chymotrypsin

4. Ribonuclease

5. Urease

6. Most Hydrolases

Name 6 enzymes that are simple proteins (composed only of amino acids)?

The three kinds of specificities of enzymes are (AGO):

1. Absolute Specificity (only one)

2. Group specificity (group of substances)

3. Optical Specificity (same group of substances ; same optical activity)

What are the three kinds of specificities of enzymes?

Absolute specificity

What kinds of specificity is observed when urease acts only on urea?

Group specificity

Enzymes acts on a group of substances that possess a particular type of linkage common to THAT group of substances, exhibit what type of specificity?

Group Specificity

What type of specificity is observed when Amylase hydrolyses the group of substances like starch, dextrin, and glycogen? (which have the same type of Glycosidic linkages (a. 1,4))

Optical Specificity

What type of specificity is observed when:

1. D-amino acid oxidase acts on D-amino acid

2. L-amino acid oxidase acts on L-amino acid

3. Maltase catalyzes hydrolysis of a but not 13-glycosides

Apoenzyme

It is described as the protein part of the enzyme molecule that is catalytically inactive and requires cofactors to become catalytically active.

1. Prosthetic

2. Cofactor

3. Coenzyme

Name the Three Non-protein enzymes.

Cofactors

It is a non-protein component of an enzymes that is characterized by the following:

1. required by some enzymes to perform their catalytic functions

2. catalytic & inorganic

3. Can be a metal ion (activators) or an organic molecule (coenzymes)

   1. some require both

4. It is a temporary reaction

5. Not tightly bound

Activators

It is a non-protein cofactor of an ezyme that is a metal ion, can be MG²+, Zn²+, Fe³+, Mn²+

Coenzymes (Cofactior; Organic)

It is a small non-protein organic molecule; a cofactor of an enzyme which aids enzymes in performing their catalytic functions.

E.g. NAD, FAD, CoQ, PP, TPP

Holoenzymes (Holo!! - active)

catalytically active enzyme-cofactor complex

Metalloenzymes (Metallo=metal)

enzymes requiring metal ions

Antienzyme (Anti=inhibit)

inhibits the action on an enzyme on a substrate

Prosthetic group (Pros for permanent)

It is an inorganic cofactor that is tightly bound (permanent) to the protein

Isoenzyme (iso versatile)

An enzyme that occurs in mutiple forms within an organism

Proenzyme or Zymogen (Zy=sigh* (inactive))

Inactive form of an enzyme.

1. Must be activated = perform catalytic functions

2. Examples

   1. Pepsinogen (product of gastric mucosa). Converted to active protein by HCL present in the gastric juice.

   2. Trypsinogen (product of the pancreas). Becomes active trypsin by eterokinase in duodenum.

   3. Chymotrypsinogen (pancreas). Active chymotrypsin in the intestine = contact with trypsin

Properties of pro-enzymes or zymogen.

Substrate

It is the chemical substance or substances upon which the enzyme acts.

Active Site

The specific area of the enzyme to which the substrate attaches during reaction.

1. Chemically uniformative names PRTC

   1. Pepsin

   2. Rennin

   3. Trypin

   4. Chymotrypsin

2. Suffix-ase to the:

   1. Name of the substance

   2. Type of reaction that is catalyzed by enzymes AMLHD

      1. Arginase (catalyze hydrolysis of arginine to ornithine and urea)

      2. Maltase (catalyze the hydrolysis of maltose to glucose)

      3. Lipase - Lipids

      4. Hydrolase (catalyzes hydrolytic reactions)

      5. Dehydrogenase (catalyzes the removal of H from a substance)

   3. Combinations of several designations XSM

      1. Xanthine Oxidase (enzyme; catalyzes oxidation of xanthine)

      2. Succinate dehyddrogenase

      3. Malate dehydrogenase

What are the three nomenclature of enzymes?

Code No. Class Name (Reaction)

1. Oxido-reductases (redox reductions)

2. Transferases (transfer of functional groups except H)

3. Hydrolases (Hydrolytic reactions)

4. Lyases (Catalyze the Non-hydrolytic removal of groups usually form double bonds)

5. Isomerases (Interconversions of Optical, Geomterical functional, or stereoisomers)

6. Ligases (Catalyzes the joining of two molecules with the breaking of a pyrophosphate bond or catalyze formation of bonds with ATP Cleavage)

Enzyme classification according to the Enzyme Commission of IUB (International Union of Biochemistry)

Lyase

Identify the type of reaction of the item below:

Histidine → Histamine + CO2

Transferase

Identify the type of reaction of the item below:

Glucose + ATP → Glucose-6-P + ADP

Hydrolase

Identify the type of reaction of the item below:

Protein→Amino Acid

Hydrolase

Identify the type of reaction of the item below:

Lactose→Glucose + Galactose

Oxidoreductase

Identify the type of reaction of the item below:

Alcohol→Aldehyde

Oxidoreductase

Identify the type of reaction of the item below:

Alcohol → Ketone

Hydrolase

Identify the type of reaction of the item below:

Fats→Fatty Acids + Glycerol

Lyase

Identify the type of reaction of the item below:

Asn→Asp+NH3

Isomerase

Identify the type of reaction of the item below:

Glyceraldehyde→3-P→DHAP

Hydrolase

Identify the type of reaction of the item below:

Starch→Glucose

Ligase

Identify the type of reaction of the item below:

Pyruvic acid+ CO2+ ATP→Oxaloacetic Acid + ADP +Pi

Ligase

Identify the type of reaction of the item below:

Acetate + CoA-SH + ATP→Acetyl-S-CoA + AMP +PPi

Lyase

Identify the type of reaction of the item below:

R-CHCH2R’→RCH=CHR’+NH2

Transferase

Identify the type of reaction of the item below:

NH3-CH-COO-+R’-CO-COO—>R-CO-COO-+NH3-CH-COO-

Oxideoreductase

Identify the type of reaction of the item below:

CH3-CH2OH→CH3CHO+2H+

Hydrolase

Identify the type of reaction of the item below:

R-O-PO3²-+H2O → ROH+HPO4²-

Isomerase

Identify the type of reaction of the item below:

L-Alanine →← D-Alanine

Key Points to Identify Reaction Types:

1. Oxidoreductases (Redox Reactions)

   1. Look for electron transfers (H⁺ or O₂ involvement).

   2. Example: Alcohol → Aldehyde or Ketone.

2. Transferases (Functional Group Transfer)

   1. Look for movement of groups like phosphate, amino, or acetyl.

   2. Example: ATP → ADP with phosphate transfer.

3. Hydrolases (Hydrolysis Reactions)

   1. Look for H₂O as a reactant and bond breaking.

   2. Example: Starch → Glucose.

4. Lyases (Non-Hydrolytic Group Removal)

   1. Look for CO₂, NH₃, or H₂O removal without oxidation.

   2. Example: Decarboxylation.

5. Isomerases (Molecular Rearrangement)

   1. Look for structural rearrangements or stereoisomer changes.

   2. Example: Glyceraldehyde-3-P → DHAP.

6. Ligases (Bond Formation with ATP)

   1. Look for ATP hydrolysis and bond formation.

   2. Example: Acetate + CoA → Acetyl-CoA

What are the key indicators of the five classification according to the IUB?