Protein and Nucleotide Metabolism Lecture by Zsolt Kovacs

These flashcards cover key concepts related to protein metabolism, hemoglobin synthesis and degradation, metabolic disorders, and nucleotide metabolism as discussed in the lecture.

What is the first step in the biosynthesis of porphyrins in mammals?

The condensation of glycine and succinyl-CoA to form δ-aminolevulinate.

Which enzyme catalyzes the condensation of glycine and succinyl-CoA?

δ-aminolevulinate synthase.

What is the role of ferrochelatase?

It catalyzes the insertion of ferrous iron into protoporphyrin to produce heme.

What is bilirubin converted to in the liver?

Bilirubin is transformed into bilirubin diglucuronide.

What causes jaundice?

Impaired liver function or blocked bile secretion, causing an accumulation of bilirubin in the blood.

Which metabolic disorder results from a deficiency of enzymes in the heme biosynthetic pathway?

Porphyrias.

What is the main characteristic of acute intermittent porphyria?

Overproduction of porphyrin precursors leading to neurological symptoms.

What is the primary source of energy buffer in skeletal muscle derived from creatine?

Phosphocreatine.

How do purine nucleotides undergo de novo synthesis?

The purine base is synthesized piece by piece directly onto a ribose-based structure.

Which enzyme catalyzes the formation of adenylate (AMP) in the salvage pathway?

Adenine phosphoribosyltransferase.

What happens to the sugars during the synthesis of deoxyribonucleotides?

The 2’-hydroxyl group in ribose is replaced by a hydrogen atom.

What is a key regulatory enzyme in pyrimidine biosynthesis?

Aspartate transcarbamoylase.

How does the regulatory mechanism of ribonucleotide reductase work?

The activity is reduced by binding of dATP and stimulated by binding of ATP.

What is the significance of hypoxanthine-guanine phosphoribosyltransferase (HGPRT) in nucleotide metabolism?

It recycles free purine bases and its deficiency leads to Lesch-Nyhan syndrome.

What is the role of creatine kinase in muscle metabolism?

It catalyzes the reaction of creatine phosphate regenerating ATP from ADP.

How do cancer therapies often target nucleotide biosynthesis?

They inhibit key enzymes required for nucleotide production, making cancer cells more susceptible.