Mila Jullig - Lecture 2

Question 1

HIV-1 protease

Answer 1

• Aspartic protease
• cuts up polyproteins of virus into final products
• very important in viral reproduction

Question 2

caspases

Answer 2

• Cysteine proteases

- used in apoptosis, but also in necrosis and inflammation

Question 3

Cathepsin D

Answer 3

• Aspartic protease
• involved in lysosomal proteolytic degradation intracellularly
• similar activity to pepsin, but narrow specificity

Question 4

calpains

Answer 4

• Cysteine proteases
• used in cell mobility and cycle progression, LTP, cell fusion, memory, apoposis, necrosis
• non-lysosomal Ca activated, neutral proteases

Question 5

Entertopeptidase

Answer 5

• Serine protease

- converts trypsinogen to trypsin

Question 6

collagenases

Answer 6

• Metalloprotease
• secreted as pro-collagenases, converted by stromelysins
• cleave peptide bonds in carious collagens

Question 7

Trypsin

Answer 7

• Serine protease
• catalyses hydrolysis of proteins
• secreted from pancreas into SI as trypsinogen
• activated by Enteropeptidase (serine) by cleavage of trypsinogen activation peptide OR catalysed by trypsin

Question 8

Matrix Metalloproteinases

Answer 8

• Metalloprotease
• ECM = provide scaffolding for cells, protect cells and signals go through ECM
• use zinc for catalysis
• secreted in pro form, with cysteine blocking zinc bining site, cleavage of this activates

Question 9

26S proteasome

Answer 9

• Threonine protease
• subunits of proteasome
• found in cytosol and/or nucleus of all eukaryotic cells
• degrades damaged or unneeded proteins

Question 10

Chymosin/rennin

Answer 10

• Aspartic protease
• secreted by chief cells in abomaum lining of calves
• found in rennet, curdles milk (hhelpful for increasing absorption)
• targets kappa casein (phosphoprotein with phosphates on OH groups of some serine - also glycosylated at some threonine - charged and hydrophillic so soluble in water)
• kappa casein solublises alpha and beta casein in micelles
• chymosin cleaves off hydrophillic portion of kappa casein => no repelling, forms meshworks

Question 11

renin

Answer 11

• Aspartic protease
• secreted by the kidney at low blood volumes
• angiotensinogen (from liver) is converted into angiotensin I (10 residues)
• (ACE in lungs and endothelial cells required to convert angiotensin Ito angiotensin II)
• Renin-Angiotensin System - used to elevate BP by increasing volume of blood plasma, lymph and interstitial fluid (by increasing na and h2o readbsorbtion) and increasing arterial vasoconstriction

Question 12

most cathepsins

Answer 12

• Cysteine proteases
• found within lysosomes, activated at low pH
• lysosomal degradation

Question 13

Thrombin

Answer 13

• Serine protease

- coagulation factor

Question 14

pepsin

Answer 14

• Aspartic protease
• one of the main digestive enzymes
• secreted as Pepsinogen from chief cells
• secretion of HCl from parietal cells lowers pH
• low pH causes unfolding and cleavage into active form

Question 15

Chymotrypsin

Answer 15

• Serine protease
• secreted from pancreas as chymotrypsin
• activated by trypsin
• helps convert protein and large peptides into amino acids

Question 16

gelatinases

Answer 16

• Metalloprotease
• secreted as pro-gellatinases, converted by M-type MP and Matrilysin
• breaks bonds in collagen

Question 17

papain

Answer 17

• Cysteine protease
• used as meat tenderiser
• catalyses reactions through…
• — deprotonation (reduction) of Cysteine 25 by Histidine 159 => stronger acid, right microenvironment
• — Cys 25 neucleophilic attack of carbonyl carbon in substrate backbone => peptide bond broken, , half substrate free
• — complex deacylated by water => remaining substrate removed and back to original state.
• metals inhibit papain activity
• preference to cleave with large hydrophobic AA in P2 position
• broad specificity, breaks bonds of basic AA

Question 18

Elastase

Answer 18

• Serine protease
• secreted from pancreas to duodenum as proelastase
• activated by trypsin
• catalyses digestion of elastin (lots in meat)

Question 19

Which two catalytic groups aren’t mentioned and why?

Answer 19

• Glutamate proteases - found in some fungi and baceria

- Aspargine peptide lyases - only class that arent hydrolases - cleave themselved. Found in viruses