1.To study the importance of creatine in muscle as a storage form of energy 2.To understand the biosynthesis of creatine 3.To study the process of creatine degradation and formation of creatinine as an end product 4.To understand the clinical importance of creatinine as a sensitive indicator of kidney function 5.To study different types of creatine kinase (CK) and their clinical importance Objectives
Overview Phosphagen is an energy- rich phosphate compound. Breakdown of a phosphagen such as creatine phosphate enables ATP (adenosine triphosphate) to be generated very quickly without oxygen. ATP is the only chemical energy which can be used directly by contracting muscles.
Three amino acids are required: Glycine Arginine Methionine (as S-adenosylmethionine) Site of biosynthesis: Step 1: Kidneys Step 2: Liver Creatine Biosynthesis
Arginine + Glycine Ornithine Amidino- transferase Guanidinoacetate SAM SAH Methyltransferase Creatine Kidneys Liver
From liver, transported to other tissues 98% are present in skeletal and heart muscles In Muscle, gets converted to the high energy source creatine phosphate (phosphocreatine) Creatine Creatine phosphate ATP ADP + H+ ATP ADP Creatine Kinase
Is a high-energy phosphate compound Acts as a storage form of energy in the muscle Provides a small but, ready source of energy during first few minutes of intense muscular contraction The amount of creatine phosphate in the body is proportional to the muscle mass
1.Creatine and creatine phosphate spontaneously form creatinine as an end product 2.Creatinine is excreted in the urine 3.Serum creatinine is a sensitive indicator of kidney disease (Kidney function test) 4.Serum creatinine increases with the impairment of kidney function Creatine Degradation
Creatine Creatine phosphate ATP ADP + H+ ATP ADP Creatine Kinase Creatinine H2OH2O Pi Plasma Glomerular filtration Urine
Normal serum creatinine level is 0.7 to 1.4 mg/dL ( µmol/L) and serum creatine level is 0.2 to 0.4mg/dL The amount of creatinine excreted is proportional to the total creatine phosphate content of the body therefore can be used to estimate muscle mass Serum creatinine is a sensitive indicator of kidney disease (Kidney function test) Because normally creatinine is rapidly removed from the blood and excreted
A typical male excretes about 15mmol of creatinine per day A decrease in muscle mass due to muscular dystrophy or paralysis leads to decreased level of creatinine in urine The amount of creatinine in urine is used as an indicator for the proper collection of 24 hours urine sample (normal urinary output is mg/kg/d)
Creatinine is an end product of nitrogen metabolism and is excreted in urine. Plasma creatinine (PCr) and creatinine clearance (CrCl) are used to assess the kidney functions. PCr is more precise than (Cr Cl)which depends on urine volume for its calculation Also PCr is fairly constant through out adult life while (CrCl) declines with aging.
CK is responsible for the generation of energy in contractile muscular tissues CK levels are changed in disorders of cardiac and skeletal muscle Creatine Creatine phosphate ATP ADP + H+ ATP ADP Creatine Kinase
1.CK is required for conversion of creatine into creatine phosphate 2.It is formed of two subunits (B & M) 3.CK has 3 isoenzymes: Skeletal muscle > 98%CK-MM,2 % CK-MB Heart muscle 70% CK-MM& 20-30%CK-MB Brain :lessCK, often CK-BB These isoenzymes can be seperated according to their physical properties,eg. using electrophoresis 3 Creatine Kinase (CK)
There are many enzymes as CK, AST, LD & ALT may be increased in muscle diseases. Plasma total CK is usually the measurement of choice(largest changes and the greatest number of cases of different aetiologies) Plasma CK is valuable in the diagnosis of myocardial infarction and some muscle diseases Increases sometimes large may occur after trauma or surgical operation, intramuscular injections, after prolonged muscular exercise.
Lippincott, Illustrated Biochemistry Bishop : Clinical Chemistry Principles, Procedures Correlation 6 th edition Lecture Notes in Clinical Biochemistry