Human Biochem Exam 1 Content

PAH

Phenylalanine Hydroxylase

What are the cofactors for PAH?

O2 and BH4

What does PAH do?

It catalyzes the conversion of phenylalanine to tyrosine

Functions of nucleotides

DNA/RNA precursor; components of NAD(H), NADP(H), CoA; high energy donors (ATP/GTP); carriers in biosynthesis; modulators of allosteric regulations of metabolism; second messangers;

Components of a nucleotide

five carbon sugar, nitrogenous base, and phosphate

Nitrogenous bases

Purines (A/G) and Pyrimidines (C/T/U)

Pyrimidines

cytosine, Thymine, and uracil

Purines

Guanine and Adenine

Nucleoside

Sugar and a base

De novo pyrimidine product

UMP

De novo pyrimidine requirements

Glutamine, Asparatate, bicarbonate, and ATP

How many ATP are required for de novo synthesis of pyrimidines

Two ATP = 1 mol UMP

How is UMP formed?

Glutamine and bicarbonate + 2 ATP and CPS-II = carbamoyl phosphate + Aspartate and Aspartate carbamoylase = carbamoyl aspartate + dihydroorotase = dihydroorotate + dihydroorotate dehydrogenase = orotate + PRPP + UMP synthase = UMP

How is CMP formed?

UMP converted to UTP (requiring 2 ATP), UTP converted to CTP (CTP synthetase and Glutamine amination - nitrogen donation), CTP to CMP (dephosphorylation)

Purine Biosynthesis Precursor

IMP

Requirements of purine biosynthesis

CO2, Glycine, Asparagine, and Glutamine, Folic Acid (THF co-factor), 5 ATP

Steps of de novo IMP

Ribose-5-P + ATP and PRS = PRPP + AmidoPRT and Glutamine =

First enzyme of IMP biosyntheis

PRS

Key Regulatory step for IMP synthesis

AmidoPRT (amidophosphoribosyltransferase)

AMP and GMP are derived from where?

IMP

Precursor for IMP?

PRPP

Amino Acids used to create Purines from IMP

Aspartate and Glutamine

Synthesis of AMP and GMP has what charge?

Net neutral for consumption and production of glucogenic substrates

De novo

build new nucleotides

Salavge

Recycle existing bases

Salvage or De Novo Purines?

Purines are salvaged, because it is less costly than rebuilding them

How are purines salvaged?

PRPP is used to add ribose and phosphate to base

Salvage or De novo for Pyrimidines?

Pyrimidine salvage is not a major pathway in vertebrates

Purine Salvage enzymes

APRT and HGPRT

Deficiency in HGPRT causes what?

Lesch-Nyhan syndrome

What is the end product of Purine degradation?

Uric Acid

What is the end product of pyrimidine degredation?

small soluble fragments (ex: ammonia, b-Ala) or other biosynthetic purposes (ex: malonyl CoA)

Degradation of Pyrimidines

Ring cleavage

Ring Cleavage

AMP to IMP

AMPD (AMP deaminase)

IMP to AMP

Adenyl Succinate

What enzyme converts Xanthie to Uric Acid?

Xanthine Oxidase (XO)

What enzyme do other organisms have to break down Uric Acid?

Uricase, which breaks down uric acid into allantoin

Level of Uric Acid in humans

6 to 7 mg/dL

Why is excretion of Uric acid important

Removes nitrogen waste from body