Lecture 9 Flashcards
Types of enzymes
Hydrolases
Transferases
Oxidoreductases
Lyases
Ligases
Isomerases
Hydrolases
catalyze hydrolysis reactions
Transferases
move a group, such as an amino group
Oxidoreductases
promote oxidation/reduction reactions
Lyases
remove a group, but not by hydrolysis
Ligases
create new bonds
Isomerases
inter-convert isomers
Naming substrates
Trivial names formed from the substrate, then the type of reaction, along with the ending: –ase
Isoenzymes
Enzymes that have evolved slightly different amino acid sequences
Act on the same substrate, but may be secreted from different types of tissues
function best at different pHs
How isoenzymes does Lactose Dehydrogenase (LDH) have?
5 isoforms
Apoenzyme
the protein portion of an enzyme
Not functional because it lacks a cofactor
Proenzyme
a non-functional form of an enzyme
can be converted into a functional form, often by hydrolysis of a group(s)
Cofactor
an inorganic species that is required for the function of an enzyme
Coenzyme
an organic cofactor
called a prosthetic group if it is tightly bound
Many coenzymes are vitamins
Enzyme units
Enzyme Activity is determined by an assay instead
indicates how much of the enzyme is functioning in the sample
Measured as U or IU of enzyme
intracellular enzymes
enzymes detected in serum
What does elevated serum enzymes indicate?
trauma
cell death caused by a disease
Creatine kinase (CK)
enzyme that phosphorylates creatine into creatine phosphate (CP)
What are the isoforms and location for Creatine Kinase?
CK-MM: found in skeletal muscles
CK-MB: found mostly in the heart
CK-BB: found mostly in the brain and smooth muscle
Lactate dehydrogenase (LDH)
enzyme that promotes the oxidation of lactate to pyruvate
Alkaline phosphatases (ALKP)
Mostly found in bone, kidneys and intestines
Promotes dephosphorylation under alkaline (basic) conditions
What essential role does ALKP play in?
bone calcification
Elevated ALKP in several bone diseases and during healing of broken bones
Which group is ALKP elevated usually?
Children, growth spurts
Acid phosphatases (ACP)
largest amount is in the prostate
Promotes de-phosphorylation under acid conditions
When is ACP elevated?
elevated in prostatic carcinoma (malignant cancer)
Phosphorylation
addition of a phosphate
done by ATP as well as other phosphate sources
Dephosphorylation
removal of a phosphate
Phosphorylation/Dephosphorylation
Regulates protein function
Can activate or inactivate
Phosphatases
Enzymes that catalyze phosphorylation/dephosphorylation
Phosphorylation/Dephosphorylation reactions are what kind of reaction?
condensation/hydrolysis reactions of esters
What enzymes are made in the liver?
Alanine amino transferase (ALT)
Aspartate amino transferase (AST)
Gamma glutamyl transferase (GGT)
Aspartate amino transferase (AST)
catalyzes a reaction between the amino acids aspartate and glutamate
important enzyme in amino acid metabolism
Alanine amino transferase (ALT)
catalyzes the conversion of alanine, an amino acid found in proteins, into pyruvate
important intermediate in cellular energy production
Elevation of Liver enzymes indicate what?
○ of hepatitis, cirrhosis, fatty liver disease, alcoholism, etc
Pancreatic enzymes
Amylase (AMY)
Lipase (LIP)
Amylase (AMY)
hydrolyzes polysaccharides to smaller polysaccharides or monosaccharides
Lipase (LIP)
hydrolyzes the two end esters of a triglyceride
Diagnostic value of enzymes
CK – muscular dystrophy, heart attacks
ALT and AST - liver disease/hepatitis
GGT – ethanol toxicity to liver
ALKP – bone diseases and bone healing
ACP – prostate cancer
LIP and AMY – pancreatitis
Prions
Diseases that are associated with a protein being the infectious agent
Immunoassays
Based on the highly specific binding of an antibody to its antigen
ELISA
Enzyme Linked ImmunoSorbent Assay
Prostate Specific Antigen (PSA) testing
ELISA screening method for prostate cancer
