Struktur Enzim

Cakupan Isi Tugas Kelompok 1. Enzyme : Introduction

a. Fungsional properties b. Enzyme Nomenclatur c. Enzyme Specificity d. Enzyme Regulation e. Activation Energy

Struktur Enzim

Apoenzyme + Coenzyme = HoloenzymeBagian protein Grup prostetik Enzim lengkap (tidak aktif) (tidak aktif) (aktif)

M+

Protein

Apoenzim Coenzim

Molekul organik

Aktivatorion logam

Substrat

Tempataktif

Apoenzyme the protein part of the enzyme molecule

– Struktur protein enzim sangat kompleks dan berfungsi menyediakan lingkungan untuk kelangsungan reaksi dengan mekanisme tertentu

– Fungsi lain adalah sebagai tempat patron (template) substrat, dan karenanya protein enzim berfungsi mengenal substrat yang dipertimbangkan menjadi dasar spesifitas enzim

Cofactor the additional chemical groups appearing in those

enzymes that are conjugated proteins.

Cofactor

These cofactors are required for enzyme activity and may consist of metal ions or complex organic molecules. Some enzymes require both types of cofactors.

Cofactors ( bukan protein) can be divided into three groups

a. yg terikat kuat pd

protein - Prosthetic group

-b. yg mudah dipisahkan)

- coenzyme ( berupa bhn organik)

- Metal Activators

Prosthetic group– In the enzyme molecule, the cofactor may be weakly

attached to the apoenzyme, or it may be tightly bound to the protein. If it is tightly bound, the cofactor is called a prosthetic group

– Example: bagian porphyrin (moiety) dari hemoprotein peroxidase dan flavin-adenine dinucleotide dalam succinic dehydrogenase

Coenzyme– When the cofactor of an enzyme is a complex

organic molecule other than a protein, the cofactor is called a coenzyme

– Example: NAD+, NADP+, tetrahydrofolic acid dan thyamin pyrophosphate

Activator– When the cofactor of an enzyme is a metal ion,

such as the ions of magnesium, zinc, ion or manganese), the cofactor is called an activator

– Examples: K+, Mn+2, Mg+2, Ca+2 dan Zn+2

Isoenzyme– Enzymes that perform the same catalytic

function in different body tissues or different organisms, but which have different sequences of amino acids in various portions of their polypeptide chain are called isoenzymes. Isoenzymes can be separated from one another by electrophoresis.

Enzyme classes .

A system of classification has

been developed that takes into account both

their reaction specificity and their substrate

specificity. Each enzyme is entered in the Enzyme

Catalogue with a four-digit Enzyme

Commission number (EC number). The first

digit indicates membership of one of the six

major classes. The next two indicate subclasses

and subsubclasses. The last digit indicates

where the enzyme belongs in the subsubclass.

.

Enzymes with similar reaction specificities

are grouped into each of the sixmajor classes

1. The oxidoreductases (class 1) catalyze the

transfer of reducing equivalents from one redox

system to another.

2.The transferases (class 2) catalyze the transfer of other groups from one molecul to another.

. Oxidoreductases and transferases generally require coenzymes (see pp.104ff.).

3. The hydrolases (class 3) are also involved in group transfer, but the acceptor is always water molecule.

4. Lyases (class 4, often also referred to as“synthases”) catalyze reactions involving eitherthe cleavage or formation of chemical bonds, with double bonds either arising of disappearing.

5. The isomerases (class 5) move groups within a molecule, without changing the gross composition of the substrate.

6. The ligation reactions catalyzed by ligases (“synthetases,” class 6) are energy-dependent and are therefore always coupled to the hydrolysis of nucleoside triphosphates.

For example,

lactate dehydrogenase(see pp. 98–101) has the EC number 1.1.1.27(class 1, oxidoreductases; subclass 1.1, CH–OHgroup as electron donor; sub-subclass 1.1.1,NAD(P)+ as electron acceptor).

ENZIM dan Kinerjanya, dipengaruhi :1.Konsentrasi Enzim

2.Konsentrasi Substrat ----- Michaelis Menten

----- Lineweaver Burk

3. Suhu

4. pH

5. Inhibitor

a. Hambatan Ireversibel

b. Hambatan Reversibel – b.1. hambatan bersaing

b.2. Hambatan tidak bersaing

c. Hambatan Alosterik

6. Kovaktor a. gugus Prosterik, b. koenzim, c. Aktivator

7. Vitamin vs Enzim

Summary