Enzymes

Enzymes: Clinical correlations

Case no. 1 for group A
An obese, middle-aged man was brought to the emergency room by police officers, who stated that the patient had been involved in an automobile accident. It appeared that he had "blacked out" and caused a collision. The patient stated that he had been short of breath and very dizzy just before the crash. Examination raised the suspicion of either a cerebrovascular accident or a myocardial infarction. The patient was admitted for observation, and a blood sample for creatine kinase (CK) and other enzyme assays was collected and forwarded to the laboratory.
Three major isozymes of CK can be detected by electrophoresis on polyacrylamide gels. The most anodic of these is known as the BB isozyme, the most cathodic is known as the MM isozyme, and the intermediate band is known as the MB isozyme (M stands for muscle and B for brain). Relate these observations to the net charge on the M and B monomers.
Since the myocardium is a muscle, is it reasonable to assume that the major isozyme of the myocardium is of the form MM?
What other enzyme assays might have been requested in the present instance?

Case no. 2 for group B

An actually ill patient was seen in the medicine clinic of a university hospital. The physical findings and much of the history were compatible with a diagnosis of acute pancreatitis and a determination of serum amylase was requested. Shortly after the serum sample reached the laboratory, the physician was informed that the serum was turbid, with no evidence of hemolysis. The technologist agreed to dilute the sample in an effort to lower the turbidity and make the analysis more reliable.

Are glycogen and cornstarch equally suitable as substrates?

when dialyzed against ethylenediamine tetra-acetic acid (EDTA), the activity of a certain amylase preparation fell to 20% of the control value. When dialzed against EDTA in the presence of starch, the activity was 66% of the control value. Can you explain these observations.
Like most other proteins, amylase can be hydrolyzed to a mixture of amino acids and smaller peptides by proteorytic enzymes. Amylase is more resistant to proteolysis in the presence of Ca++ than in its absence. Explain this distinction.

Case no. 3 for group C

A 36-year-old man was first seen in the emergency room at 6 pm. He stated that at approximately 4:15 pm that afternoon he had felt a sharp sever pain that increased in intensity for about 45 min and that had since remained constant. He had never before experienced pain of this type. He was sitting quite still in a chair, and when he moved to an examining table, he stated that the pain worsened. He looked pale, sweaty, and sick. His respirations were shallow, and he stated that deeper breathing was more painful. His blood pressure was 100/60 mm Hg (13.3/7.9 kPa), his pulse was 110 and regular, and his temperature was 37.5 C. Significant physical findings were limited to the abdomen, which was rigid to palpation. There was tenderness (pain) when the epigastrium was firmly pressed; when the examiner hand was suddenly removed, the pain was momentarily increased (rebound tenderness).
The patient was admitted with orders that he be given nothing by mouth. An intravenous catheter was inserted, and he was given- a mixture glucose and saline solution' A nasogastric tube was employed for continuous aspiration stomach contents.
Which digestive enzymes are produced in the pancreas? can they be found in the serum?
Would treatment with glucose and saline solution completely correct the electrolyte abnormalities?
Are there natural inhibitors of any component of the pancreatic secretions? Do these occur in humans?
enumerate the common causative factors acute pancreatitis


Case no. 4 for group D
A 1-year-old girl was brought to her pediatricians office with concerns about her development. She had an uncomplicated birth outside the United States at term. The mother reports that the baby is not achieving the normal milestones for a baby of her age. She also reports an unusual odor to her urine and some areas of hypopigmentation on her skin and hair. On exam, the girl is noted to have some muscle hypotonia and microcephaly. The urine collected is found to have a mousy odor.
What is the most likely diagnosis?
What is the biochemical basis of the hypopigmented skin and hair?

Case no. 5 for group E

A 2-year-old child has failure to thrive. The child exhibits convulsions. On physical examination there is hepatomegaly along with multiple ecchymoses of various ages of the skin. Laboratory studies show a blood glucose of 31 mg/dL. Liver biopsy was performed and microscopic examination shows hepatocytes filled with clear vacuoles that stain positively for glycogen. Which of the following inborn errors of metabolism is this child most likely to have? Explain your answer.

McArdle syndrome

Hurler syndrome
Tay-Sachs disease
Von Gierke disease
Pompe disease