Mod.A. Bio Lec1: Enzymes Flashcards
Enzymes are:
are complex protein : composed of protein PLUS a nonprotein
- الجزء البروتيني → يسمى Apoenzyme * الجزء الغير بروتيني → يسمى Prosthetic group / Coenzyme / Cofactor
- دورها : biological catalysts.: Increase the rate of reaction by lowering the energy of activation.
- أثناء التفاعلات : 1- are neither consumed nor produced during the reaction.
2- catalyze energetically feasible reactions only. بمعنى أن هناك تفاعل واحد قابل للتنفيذ
- التخصصية : often show a high specificity
toward one substrate
Enzyme Specificity Types :
1- Absolute 2- Group 3- Linkage
Active site
where binding with a substrate takes place
- Including
1- contact site for binding a substrate and
2- catalytic site
Allosteric site
المادة المرتبطة:- Allosteric Regulator :
وهي molecules structurally dissimilar substrate bound to this site
- نتيجة ارتباطها could change the enzyme configuration
ENZYME REGULATION is by
1- allosteric regulation
2- covalent modification
ALLOSTERIC REGULATION
Allosteric regulation occurs when a non-substrate molecule ( تسمى Allosteric regulators ) binds or modifies an allosteric site, which is a site other than the active site
- Allosteric regulators can be inhibitors or activators .
COVALENT MODIFICATION
- كيف تتم : typically occurs by the addition of a phosphate group to one or more of the
enzymes amino acids - النتيجة : if the phosphate is added in a hydrophobic region of the enzyme,
1- it makes that region hydrophilic. because phosphate carries a negative charge.
2- The protein twists, thereby inducing the enzyme to change its shape.
and this can expose or hide the active site. بمعنى The shape change can result in the activation or inactivation of an enzyme.
How does substrate concentration affect enzymatic activity ?
at constant enzyme concentration :
The rate of reaction increases as substrate concentration increases
Maximum activity occurs when the enzyme is saturated.
Km
is the substrate concentration at which the reaction rate is half of Biochemical reactions
Km describes an affinity of the enzyme to its substrate :
indirect proportionality العلاقة بينهما علاقة عكسية
Clinical utility of enzymes:
1- Diagnosis and follow up of diseases
( Non Functional Plasma enzymes)
2- Therapeutic agents
FACTORS DETERMINING CLINICAL UTILITY
1- Organ and tissue distribution of enzymes
2- Intracellular localization of enzymes
3- Timing and magnitude of elevation
4- Way of enzyme elimination from blood
Enzyme increases are usually related to
leakage of enzymes from damaged cells
Enzyme assays are done by :
1- the catalytic activity of the enzyme (most used)
2- the concentration of the enzyme
Katal (catalytic activity)
is the number of mole of substrate transformed
per second per litre of sample.
وحدة قياسها : International Unit ( U/L ) .
Amylase and lipase indicate :
Pancreatitis
Acid phosphatase indicates :
Prostate cancer
