BIOCHEMISTRY, BIOMEDICINE & PHARMACEUTICS

Overview of the Heme Metabolism In this page, we will review the biological importance of heme, heme biosynthesis, regulation of heme synthesis. The disorder of heme metabolism,  porphyria definition, classification, diagnosis, and treatments discussed elsewhere and a link for the page is provided below. You can also review the practice question by clicking the link provided below Page Links  Heme Biosynthesis and Regulation  Disorders of Heme Biosynthesis & Porphyria Multiple Choice Question in Heme Metabolism and Porphyria Biological Importance of Heme  - Oxygen transport (Hemoglobin) & Storage  (Myoglobin) - Electron carrier in Electron Transport Chain  (Cytochromes) - Prosthetic group of various enzyme - Deficiency of the enzyme causes porphyrias Next Page >> Biosynthetic Pathway for the Synthesis of Heme 

Pheochromocytoma is a catecholamine-producing tumor - Catecholamine producing tumors arising from chromaffin tissues - Rare disorders with an annual detection rate of 2 to 5 per million.  - Hypertension is the most common symptom of Pheochromocytoma - Other symptoms include palpitation, diaphoresis  - Most pheochromocytoma are benign with only 15% of adrenal tumors and 35% of extra-adrenal tumors being malignant - Approximately 30% to 40% are hereditary. Mutation of the genes encoding succinate dehydrogenase, MYC associated factor X are some of the identified susceptibility genes.  Biochemical Basis - Mechanisms of excessive production of catecholamines in the patients with pheochromocytoma is unclear - the presence of tumors leads to a relatively large increase in the production of O-methylated metabolites.  - Multiple Endocrine Neoplasia syndromes (MEN) mainly MEN2A and MEN 2B manifest as pheochromocytoma in addition to thyroid carcinoma and others. - MEN 2A (...

Branched Chain Amino Acid Metabolism and Maple Syrup Urine Disease  Metabolic Pathway of  Branched Chain Amino Acids (Leucine, Isoleucine, and Valine) Transamination of Branched Chain Amino Acid - The first step in the catabolism of branched-chain amino acids including leucine, isoleucine, and valine  - Catalyzed by an enzyme branched-chain amino acid aminotransferase - Conversion of branched-chain amino acids to respective branched-chain keto acids - The amino group is transferred to alpha-ketoglutarate to form glutamate Decarboxylation of Branched Chain Keto Acids - Catalyzed by enzyme branch chain keto acid dehydrogenase complex (BCKDC) - BCKDC consists of four different subunits E1- α,  E1-β, E2 & E3  - E1-  α2 β2 tetramer is a thiamine pyrophosphate dependent decarboxylase encoded by  BCKDHA & BCKDHB  - E2 is dihydrolipoamide branched-chain transacylase encoded by  DBT - E3 is a flavoprotein dihydrolipoamide dehydrogenase en...