Understanding Proteolytic Activation: The Key Mechanism of Enzyme Regulation

the next mechanism of enzyme regulation that we're going to focus on is known as proteolytic activation or proteolytic

cleavage or sometimes known as proteolysis now what exactly is this process of

proteolysis well sometimes our cell produce enzymes initially in their inactive form and these inactive enzymes

precursor enzymes are known as pro-enzymes or zymogens and we'll see many different examples in just a moment

now to actually activate these enzymes we have to basically cleave the enzymes as specific peptide bonds so sometimes

we cleave one peptide bond sometimes we cleave many peptide bonds but the end result is the same exact when our

xymogen under goes proteolytic activation proteolytic cleavage by some type of protease we basically produce

the fully functional form of that enzyme now when we discussed the process of phosphorilation we said that only those

enzymes and proteins that are found inside our cells can actually be controlled via the process of

phosphorilation and that's because phosphorilation actually requires the presence of ATP and ATP molecules are

found abundantly only inside ourselves so that means phosphorilation can control only those enzymes and proteins

which exist inside our cells on the other hand unlike phosphorilation proteolytic activation does not require

ATP and what that means those enzymes and proteins which are found outside ourselves in the extracellular

environment can readily undergo the process of proteolytic activation now unlike alisic regulation

and coent modification such as phosphorilation which can take place many times on any given enzyme when a

zymogen under GO proteolytic activation it will only undergo this process once in the lifetime of that enzyme so once

again proteolytic activation does not require ATP adenosine triphosphate and so it can readily take place outside the

cells in addition enzymatic proteolysis only occurs once in the lifetime of that enzyme now the next question I want to

explore is what are some examples of enzymes biological proteins found inside our body that utilize the process of

proteolytic Activation so I've listed six different categories six different types of enzymes so category one and two

are going to focus on in much more detail in the next several lectures and 3 to six we're going to focus briefly

only in this lecture so let's begin with one digestive enzyme so whenever we ingest different types of food particles

we ingest these macromolecules so proteins carbohydrates lipids and it's the function of these digestive enzymes

to basically break down these large macromolecules into smaller food particles that can be ingested by the

individual cells and these digestive enzymes are initially created in their xymogen form

and that's important because we don't want the digestive enzymes to be activated at all times we only want to

activate these zymogens these digestive enzymes when we're actually digesting when we actually eat the food so we have

these two organs we have the pancreas and the stomach that basically synthesize a variety of different types

of zymogens and activate these zymogens we have to undergo the process of proteolytic cleavage proteolytic

activation and only then when we activate these zymogens can these enzymes actually function and digest

breakdown all the different types of macromolecules that we ingest into our body now some examples of digestive

enzymes in their zymogen form are listed on the board so we have TR cinogen which is the zymogen form of TR

we have kyogen which is a zymogen form of kyin we have pepsinogen we have prolase and we have

procarboxypeptidase and again we'll talk about these in much more detail in the next two or three lectures now let's

move on to the blood clotting enzyme so inside our body we have the process we call the blood clot Cascade and what

this basically involves is the protolytic activation of many different types of zymogens into many different

types of active enzymes which basically help us produce those proteins which are involved in creating the clog when for

example there's some type of trauma to blood vessel inside our body so when we experience trauma or some type of cut to

the blood vessels our body initiates a response that involves a Cascade of proteolytic cleavages that ultimately

produces enzymes and proteins which are responsible for basically sealing off that cut in that trauma area now one

example that we're going to look at in the next several lecturas is prothrombin this is a very important zymogen that is

activated into the thrombin which basically is needed to produce those fibin molecules that essentially form

that clog now let's discuss 3 four five and six so we have hormon horm monal enzymes we have a process known as osis

or program cell death we have a very important fibrous protein that is found in Bone and Skin basically that is a

component of the extracellular environment known as collagen and then we're going to briefly look at

Developmental and remodeling processes so number three there are many hormones inside our body that are examples of

zymogens and these zymogens must be activated via prote activation and these hormones are known as proor hormones so

one example of such a hormone that is activated via proteolytic activation is insulin so many hormones are synthesized

in their zymogen form and must be activated via the process of proteolytic cleavage and one common example is

insulin and this is the hormone that is basically used to regulate the glucose level the sugar level in our blood so

our cells first synthesize insulin in the preproinsulin form and preproinsulin must undergo a single proteolytic

cleavage at a single side to basically produce proinsulin but proinsulin is not yet a fully functional enzyme Pro

insulin then under goes two proteolytic cleavages to essentially form the active form known as insulin and only then can

insulin actually lit its response number four the process of eposis and we spoke about this process in detail when

we discussed biology so we said that eposis is known as program cell death this is basically when a set of special

enzymes initiate the process of cell death now why would we ever want to actually kill off our cells what well

one reason if is if um is if our cell is infected by some type of pathogen if we have an infected cell we don't want that

infected cell to infect other healthy cells and so we want to kill off that cell and this is the process that helps

us basically kill off that cell also when the embryo is developing sometimes we actually want to kill off certain

cells in a certain area for instance when we develop the fingers and the toes to actually develop these digits we have

to destroy the cells in between these areas to basically go from this to this and this process is a result of

eposis so our cells synthesize these zymogens we call procaspases and these procaspases

undergo proteolytic activation to form their active form cast spaces and the cast spaces are these enzymes

responsible for activating the process of apotosis and again we want to undergo apotosis in one of two instances if we

have infected cells or if we want to stimulate the proper embryological development in that developing embryo

now let's move on to five and six so the most common type of fibrous protein that is found inside our body for example

it's found in bone it's found in skin and it's generally found in the areas surrounding our cells so the extracell

environment this fibrous protein as you might know is collagen but collagen must be activated from its

pro-enzyme form from its xogen form and the xogen form is known as procollagen in fact this leads us

directly into six we have another enzyme known as collagenase which is actually responsible for activating the

procollagen into collagen and so uh collagenase is the enzyme that catalyzes the cleavage of peptide Bonds in

collagen and this can either actually activate that collagen molecule or it can break down that collagen molecule

and destroy that collagen structure and this process is important in remodeling of the extracellular environment as well

as the development of the embryo so collagenase can be used to activate collagen as well as breakdown collagen

during the process of uh embryological devel uh development as well as the remodeling of the extracellular

environment and just like collagen exists in a xymogen form we call procollagen uh collagenase also exists

an enzymogenes so we have all these different types of enzymes found inside our body which

depend on proteolytic activation to actually be activated and to exist in their fully functional form and in the

next several lectures we're going to focus on digestive enzymes as well as blood clotting enzymes