Enzymes: Introduction

Most of the history of biochemistry is the history of enzyme research. Enzyme research history can be traced back to 1700 as people suspected how meat digested in the stomach. Louis Pasteur, during 1850 postulated that fermentation of sugar to alcohol by yeast and he named “ferments” for responsible molecules. In 1897 Eduard Buchner discovered that cell-free yeast extracts accountable for fermentation of sugar to alcohol. Later, Frederik W. Kuhne coined the name “ENZYME.” There are many kinds of research afterward in the field of enzymology.

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Definition:

Enzymes are biomolecules, and they speed up the rate of chemical reactions both in vivo and in vitro.

They act as biocatalyst for various biochemical reactions taking place in our bodies. The rate of biochemical reactions is millions of times faster [10⁶ or more] in enzyme-catalyzed reactions compared to that of a noncatalyzed reaction.  Enzymes are essential for all the processes taking place in our body like digestion, metabolism, DNA replication, transcription, translation, etc… Many diseases like inborn errors of metabolism, nutritional disorders are due to defect or deficiency of enzymes.

Characteristics of enzymes

All enzymes are proteins, except ribozymes. Enzymes neither consumed nor permanently altered in any chemical reactions. They transiently involved in a chemical reaction by combining with substrates ad later, they come out as the same enzymes and products. They exhibit specificities like absolute, group, and stereospecificity. Many enzymes may contain or require additional prosthetic groups such as coenzymes or cofactors.

Enzyme nomenclature

Enzymes usually named with a suffix ends with “ase” after the name of the substrate it acts. But still many enzymes have the older name as pepsin, trypsin, amylase. International union of biochemistry and molecular biology [IUBMB] came up with a unique code number and name for each enzyme, and it is called enzyme commission number or enzyme code number.

Enzyme classification

Enzymes are classified by the reaction they catalyze. There are six classes of enzymes.

1. Oxidoreductases
2. Transferases
3. Hydrolases
4. Lyases
5. Isomerases
6. Ligases

Enzyme commission/ code number

An enzyme code number is a four-digit number and begins with EC. The first digit represents the class of enzymes (one of 6 classes). The second digit represents a subclass of the enzyme or type of group involved in the reaction. The third digit represents the sub-subclass or acceptor of the group in the reaction. The fourth digit represents a serial number of an enzyme in that list.

EC 1.1.1.1 [Alcohol dehydrogenase]

EC 1 means this enzyme belongs to class 1 enzymes that are oxidoreductase. EC 1.1 means group involved the reaction catalyzed by this group of enzymes [EC 1.1 series] is CH-OH. EC 1.1.1 means acceptor molecule is NAD+ or NADP+ EC 1.1.1.1 the last digit represents a serial number that is the first enzyme in EC 1.1.1 series

EC 2.7.1.1 [Hexokinase]

EC 2 means this enzyme belongs to class 2 enzymes that are transferase. EC 2.7 means group involved the reaction catalyzed by this group of enzymes [EC 1.1 series] is the phosphorous-containing group. EC 2.7.1 means acceptor is alcohol group EC 2.7.1.1   First enzyme in EC 2.7.1 series that is hexokinase. EC 2.7.1.2   Second enzyme in EC 2.7.1 series that is glucokinase EC 2.7.1.3   Third enzyme in EC 2.7.1 series that is ketohexokinase