A. Due to Carboxyl Group

1. Decarboxylation: The amino acids will undergo alpha decarboxylation to form the corresponding amine (Fig.1). Thus some important amines are produced from amino acids. For example,

 Histidine → Histamine + CO2

 Tyrosine → Tyramine + CO2

 Tryptophan → Tryptamine + CO2

Lysine → Cadaverine + CO2

Glutamic acid → Gamma amino butyric acid (GABA) + CO2

Fig1. Decarboxylation of amino acid

2. Amide Formation: The -COOH group of dicarboxylic amino acids (other than alpha carboxyl) can combine with ammonia to form the corresponding amide. For example,

 Aspartic acid + NH3 → Asparagine

Glutamic acid + NH3 → Glutamine (Fig.2)

Fig2. Formation of glutamine

These amides are also components of protein structure. The amide group of glutamine serves as the source of nitrogen for nucleic acid synthesis.

B. Reactions Due to Amino Group

3. Transamination: The alpha amino group of amino acid can be transferred to alpha keto acid to form the corresponding new amino acid and alpha keto acid (Fig. 3). This is an important reaction in the body for the inter-conversion of amino acids and for synthesis of non-essential amino acids.

Fig3. Transamination reaction

 4. Oxidative Deamination: The alpha amino group is removed from the amino acid to form the corresponding keto acid and ammonia.

In the body, Glutamic acid is the most common amino acid to undergo oxidative deamination.

5. Formation of carbamino compound: Carbon dioxide adds to the alpha amino group of amino acids to form carbamino compounds. The reaction occurs at alkaline pH and serves as a mechanism for the transport of carbon dioxide from tissues to the lungs by hemoglobin.

Hb—NH2 + CO2 → Hb—NH—COOH (Carbamino-Hb)

C. Reactions Due to Side Chains

6. Transmethylation: The methyl group of Methionine, after activation, may be transferred to an acceptor which becomes methylated.

Methionine + Acceptor → Methylated Acceptor + Homocysteine

7. Ester formation by the OH group: The hydroxy amino acids can form esters with phosphoric acid. In this manner the Serine and Threonine residues of proteins are involved in the formation of phosphoproteins. Similarly these hydroxyl groups can form O-glycosidic bonds with carbohydrate residues to form glycoproteins.

 8. Reaction of the amide group: The amide groups of Glutamine and Asparagine can form N glycosidic bonds with carbohydrate residues to form glycoproteins.

9. Reactions of SH group: Cysteine has a sulfhydryl (SH) group and it can form a disulphide (S-S) bond with another cysteine residue. The two cysteine residues can connect two polypeptide chains by the formation of interchain disulphide bonds or links (Fig. 4). The dimer formed by two cysteine residues is sometimes called Cystine or Dicysteine.

Fig4. Formation of disulphide bridge

اخر الاخبار

اخبار العتبة العباسية المقدسة

العتبة العباسية المقدسة تنظّم محاضرة توعوية لطالبات كلية الأسوة للبنات في باكستان

الهيأة العليا لإحياء التراث تقيم دورة متخصّصة عن الفقه الكلامي

قسم التطوير يشرع بمقابلة المتقدمين للانضمام إلى أكاديمية التطوير الإداري

قسم الشؤون الفكرية يعلن انضمام جامعة كربلاء إلى المستودع الرقمي العراقي للأطاريح

المزيد

الآخبار الصحية

اختراع صيني.. لاصق يصلح كسور العظام خلال دقائق

اكتشاف حلقات عملاقة من الحمض النووي.. تقلل خطر السرطان

آباء أميركيون يطالبون بتنظيم روبوتات الدردشة لحماية الأطفال ؟

4 إشارات من القلب لا يجب تجاهلها أبدا

المزيد

الآخبار التكنلوجية

"تحليل المحادثات" يكشف كيف يستخدم الناس تشات جي بي تي

الدخان يكشف المستور.. التحنيط بدأ خارج مصر

مشهد مدهش للأرض من الفضاء.. جمجمة بيولوجية بعينين محدّقتين!

أول قطار يعمل بالهيدروجين في أميركا يدخل الخدمة رسميًا

المزيد

مواضيع ذات صلة

The Chemical Nature of RNA Differs From That of DNA

DNA Provides A Template For Replication & Transcription

DNA Can be Reversibly Denatured & Specifically Renatured, Both in the Test Tube & in Living Cells

DNA Contains Four Distinct Deoxynucleotides

Overproduction of Pyrimidine Catabolites

Disorders of Purine Metabolism

Biochemical Characteristics and Biological Function of Cardiac Natriuretic Peptides

The Deoxyribonucleosides of Uracil & Cytosine are Salvaged

Biosynthesis of Pyrimidine Nucleotides

Hepatic Purine Biosynthesis is Stringently Regulated

Inosine Monophosphate (IMP) is Synthesized From Amphibolic Intermediates

DNA & RNA are Polynucleotides