Metabolic Pathways Pt. 2

Non-competitive Inhibition: Feedback Inhibition/End Product Inhibition

Threonine => Isolencine Pathway

Threonine => Isolencine Pathway

1) Threonine is de-aminated (in the cytoplasm/plastid) => forms intermediate α-ketobutyrate.

2) α-ketobutyrate => enters branched aa pathway => combines w/ pyruvate => forming a larger carbon skeleton.

3) C-Skel => altered through several enzyme-catalyzed steps => produce the precursor 2-keto-3-methylvalerate

4) Precursor undergoes transamination, receiving an amino group to form isoleucine

5) => Isoleucine inhibits 1st enzyme in the pathway via feedback inhibition => prevent overproduction

How to turn Pre-pro Insulin into Mature Functional Insulin

• insulin is going to be secreted (extracellular protein) => signal sequence of the mRNA goes into the ER via translation by ribosome (allows for recognition)

• => polypeptide moves through translocon and into the ER Lumen => translated => end of signal sequence (after 24aa) is cleaved by signal peptidase in ER

• After chopping, the rest is called “Pro-Insulin”

• PI goes to Golgi => packaged in a secretory vesicle => other enzymes with them chop off the C-peptide

• => Mature insulin after clip of C-peptide.

• Secretory vesicle sitting in B-cells of the pancreas => released when your blood sugar is low

Define Non-conjugated proteins

• folded polypeptides without any additional chemical groups attached

• derive all structural & functional properties from the 20 standard amino acids and their various interactions

• versatility of amino acid chem => non-conjugated proteins r cool

Define Conjugated proteins

• proteins that contain one or more non-protein components called prosthetic groups

• Prosthetic Groups e.g.: metal ions, organic molecules, etc.

• Pro Groups expand the functional capabilities of proteins beyond what can be achieved with just amino acids

Protein Modification: Explain Proteolysis

• the breaking of the polypeptide chain through hydrolysis of peptide bond(s)

• => activates the protein

Protein Modification: Explain Phosphorylation

• taking off or putting on a phosphate group

• => can activate or inactivate the protein

Protein Modification: Explain Glycosylation

• process of adding carbohydrate chains to proteins

• primarily occurs in the ER and Golgi

• unique carb patterns=> cells to recognize and bind to one another

Protein Modification: Ubiquitination

• process of attaching a small protein called a ubiquitin => acts as a destroy signal on protein

Protein Modification: Lipidation

• process in which a lipid molecule is attached to a protein

• => increases the hydrophobicity of the protein