When early workers isolated certain enzymes, whimsical names were given. Some of these, such as Pepsin, Trypsin, Chymotrypsin, etc. are still used. Later, it was agreed to call the enzymes by adding the suffix "-ase" to the substrate. Thus, enzyme Lactase acts on the substrate lactose, and the products glucose and galactose are formed. Enzymes that hydrolyse starch (amylose) are termed as amylases; those that dehydrogenate the substrates are called dehydrogenases. These are known as the trivial names of the enzymes.

IUBMB System of Classification

International Union of Biochemistry and Molecular Biology (IUBMB) in 1964, (modified in 1972 and 1978), suggested the IUBMB system of nomenclature of enzymes. It is complex and cumbersome; but unambiguous. As per this system, the name starts with EC (enzyme class) followed by 4 digits.

 First digit represents the class

 Second digit stands for the subclass

 Third digit is the sub-subclass or subgroup

 Fourth digit gives the number of the particular enzyme in the list.

The enzymes are grouped into following six major classes (Box1).

Box1. Classification of Enzymes

• Class 1: Oxidoreductases

 This group of enzymes will catalyse oxidation of one substrate with simultaneous reduction of another substrate or co-enzyme. This may be represented as

AH₂ + B -------------→ A + BH₂

for example,

 Alcohol + NAD⁺ ----→ Aldehyde + NADH + H⁺

The enzyme is Alcohol dehydrogenase; IUB name is Alcohol-NAD-oxidoreductase; Code number is EC.1.1.1.1. Oxidoreductases may also oxidise substrates by adding oxygen, e.g. oxidases, oxygenases and dehydrogenases.

• Class 2: Transferases

This class of enzymes transfers one group (other than hydrogen) from the substrate to another substrate. This may be represented as

 A-R + B → A + B-R , For example,

Hexose + ATP → Hexose-6-phosphate + ADP

The name of enzyme is Hexokinase and systematic name is ATP-Hexose--6-phosphate transferase.

• Class 3: Hydrolases

This class of enzymes can hydrolyse ester, ether, peptide or glycosidic bonds by adding water and then breaking the bond.

Acetyl choline + H₂O --------→ Choline + acetate

The enzyme is Acetyl choline esterase or Acetyl choline hydrolase (systematic). All digestive enzymes are hydrolases.

• Class 4: Lyases

These enzymes can remove groups from substrates or break bonds by mechanisms other than hydrolysis. For example,

 Fructose-1,6-bisphosphate → Glyceraldehyde-3-phosphate +dihydroxy acetone phosphate

The enzyme is Aldolase .

• Class 5: Isomerases

 These enzymes can produce optical, geometric or positional isomers of substrates. Racemases, epimerases, cis-trans isomerases are examples.

Glyceraldehyde-3-phosphate → Di-hydroxy-acetone-phosphate

 Enzyme is Triose phosphate isomerase.

• Class 6: Ligases

These enzymes link two substrates together, usually with the simultaneous hydrolysis of ATP, (Latin, Ligare = to bind). For example,

Acetyl CoA + CO₂ + ATP → Malonyl CoA + ADP + Pi

Enzyme is Acetyl CoA carboxylase.

A summary of classification is given in Box 1. The differences between synthetase and synthase are shown in Box2.

Box2. Synthetase and Synthase are Different

اخر الاخبار

اخبار العتبة العباسية المقدسة

شعبة متابعة الأداء تنظم محاضرة تربوية لمتطوعات مجمع العلقمي استعدادًا لزيارة الأربعين

شعبة الحرم الشريف تكثف استعداداتها لتقديم خدمات متنوعة لزائري الأربعين

قسم الشؤون الفكرية يفتتح محطتين ثقافيتين في ذي قار لخدمة زائري الأربعين

العتبة العباسية المقدسة تعقد ملتقى خاصًا لمنتسبيها العاملين في مراكز إرشاد التائهين خلال زيارة الأربعين

المزيد

الآخبار الصحية

علامات فارقة بين النوبة أو السكتة القلبية.. ماهي؟

الفلفل الأحمر.. سعرات حرارية منخفضة وفوائد صحية عديدة

8 أعراض إذا شعرت بها.. اذهب للطوارئ فورا !

تعرف على أكثر 8 أماكن اتساخا في المنزل

المزيد

الآخبار التكنلوجية

إنتاج الهيدروجين الأخضر في البحر.. هذه أحدث الدراسات

"ناسا" تخطط لبناء مفاعل نووي على سطح القمر !

ابتكار ومواهب وأموال.. مارك زوكربيرغ يعلن الحرب على أبل

عودة التعاون الفضائي بين روسيا وأميركا.. وبحث ملفات "هامة"

المزيد

مواضيع ذات صلة

Mode of Action of Enzymes

Co-Enzymes

Regulatory Covalent Modifications can be Reversible or Irreversible

Allosteric Effectors Regulate Certain Enzymes

الأهمية الحيوية الطبية للأنزيمات

انزیم ( Glutamate Pyruvate Transaminase or Alanine Transaminas) GPT or ALT

أنزيم GOT ( AST ) (Glutamate Oxaloacetate Transaminase or Aspartate Transaminase)

كيف يعمل الأنزيم

فرضية القفل والمفتاح Lock and Key hypothesis

تصنيف الانزيمات Classification of Enzymes

الانزيمات Enzymes

Initial Considerations and Primary Recovery