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A sample of liver tissue was from a deceased patient geneticallydeficient in ONE of the enzymes of carbohydrate metabolism. Theliver sample had the following characteristics. 1) Homogenatesdegraded glycogen to glucose-6-phosphate. 2) Homogenates did notsynthesize glycogen from any sugar and could not utilize galactoseas a carbon source for energy. 3) Glucose 6-phosphate was obtainedfrom lactate, as was galactose. Provide a single enzyme deficiencythat could explain the results. You must justify your answer. Whengrowing on lactose, how much energy in the form of ATP could beobtained assuming the malate-aspartate shuttle system wasemployed?

enzyme answer Is not glycogen synthase

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Deanna HettingerLv2
28 Sep 2019
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Related questions

Glycogen StorageDiseases

Glycogen storage diseases are so namedbecause a hallmark of the diseases is impaired glycogen storage dueto a deficiency of one of the enzymes involved in either glycogensynthesis or glycogen degradation. Several kinds of glycogenstorage diseases have been identified so far. Each type ischaracterized by the lack of a specific enzyme. An understanding ofglycogen metabolism is essential in the proper treatment of thisdisease, and identification of the deficient enzyme is requiredbefore a treatment protocol can be designed.

Your patient is a fifteen-year-oldCaucasian male named Joe K. Joe can’t perform any kind of strenuousexercise. During his physical education classes, Joe could not keepup with his classmates and often suffered painful muscle cramps ifhe did attempt to exercise. He appeared to be normal if at rest orperforming light to moderate exercise. A physical examinationreveals that his liver appears to be normal in size, but hismuscles are flabby and poorly developed. A fasting glucose testshowed that Joe was not hypo- or hyperglycemic. A number ofbiochemical tests were carried out to identify the type of glycogenstorage disease in this patient.

Questions

1. You decide to try Joe’s response to glucagon. This testconsists of injecting a high dose of glucagon intravenously andthen drawing samples of blood periodically and measuring theglucose content of the samples. After the glucagon injection, Joe’sblood sugar rises dramatically. Is this the response you wouldexpect in a normal person? Explain.

2. Liver and musclebiopsies are taken from Joe and analyzed.

The biopsies revealed that glycogencontent in the liver is normal, but muscle glycogen content iselevated. The biochemical structure of glycogen in both tissuesappears to be normal. Suggest some possible explanations for theseobservations.

3. Next, you do another testwhere you have Joe perform ischemic exercise for as long as he isable to do so.

The ischemic exercise consists of thepatient squeezing a hand dynamometer at maximal strength for aspecific period of time, usually 1 minute, with an occlusionpressure cuff, which is placed on the upper arm and set at 250mmHg, blocking blood flow to the exercising arm. Blood is withdrawnfrom the patient every few minutes or so during the exerciseperiod.

a. Joe’s blood samples are tested forlactate and compared with a control sample of a patient who doesnot suffer from a glycogen storage disease. The results are shownin the plot to the right. Why does lactate concentration increasein the normal patient?

b. Why is there no correspondingincrease in Joe’s lactate concentration?

4. Urine tests after Joe has completedhis exercise reveal the presence of myoglobin in his urine.Myoglobin isn’t normally found in the urine, but in muscle cells.Why does Joe suffer from myoglobinuria following ischemicexercise?

5. Joe’s enzyme deficiency does notcause him to suffer from either hypo- or hyperglycemia. Explainwhy.

6. As a treatment, you tell Joe thatthe best thing he can do is to avoid strenuous exercise. If he doeswish to exercise, you advise him to consume sports drinkscontaining glucose or fructose frequently while exercising. Whywould this help alleviate Joe’s suffering during exercise?

i need question number nine please

Case Study Section 2 – glycolysis
Based on “Monday at the Metabolic Clinic, Adventures in Glycolysis” by Nancy Boury (National Center for Case Study Teaching in Science)

Background:
You have been chosen for a very competitive undergraduate clinical internship at St. Visintainer’s Hospital and Metabolic Clinic working with Dr. Saccharo, an expert in enzyme deficiency disorders related to glycolysis. Before your first day Dr. Saccharo has asked that you review the reactions of glycolysis and the concept of isoenzymes.

Recall that isoenzymes are groups of enzymes that catalyze the same reaction in that they use the same reactants to product the same products. They may have different genes, tissue expression, developmental timing of expression, and affinities for their substrates. As an example, phosphofructokinase-1 has 3 isoenzyme forms: PFK-L is expressed in the liver and the gene is found on chromosome 21; PFK-M is expressed in the muscle and the gene is found on chromosome 12; and PFK-P is expressed in platelets and the gene is found on chromosome 10.

Question 1:
If a person would be deficient in all 3 forms of PFK-1, this person would .
A. Have lower than normal glycogen stores.
B. Have more mitochondrial activity than normal.
C. Be dead.
D. Produce more energy per glucose molecule because glycolysis would be unregulated.

It is now Monday morning and you are ready to start seeing patients with Dr. Saccharo.

Patient 1:
Ann is a teenager and avid golfer who was referred to the clinic after being refused at the blood drive and tiring easily on the high school golf course during practice. Ann is examined and a blood sample was obtained for analysis of a glycolysis related metabolic panel. The results of her panel is below (levels: + = normal, - = decreased; ++= increased):
Blood Metabolic Panel
Blood Glucose +
Glucose-6-phosphate ++
Fructose-6-phosphate ++
Fructose-1,6,bisphosphate ++
Glyceraldehyde-3-phosphate ++
1,3-bisphosphoglycerate ++
Phosphoenolpyruvate ++
Pyruvate -
ATP -
Red Blood Cell Concentration -
Question 2:
Assuming that Dr. Saccharo is correctly assuming that Ann has a defect in glycolysis, what glycolytic enzyme is the most likely to have the defect based on the blood metabolic profile?
A. Hexokinase
B. Phosphofructokinase
C. Triose Phosphate Isomerase
D. Pyruvate Kinase
E. Aldolase

Patient 2:
Marie is a 32-year-old mother of three complaining of fatigue and muscle cramps with exercise. She had always blamed her intolerance to exercise on her sedentary lifestyle. However, she recently joined a gym and after a week of aerobics classes went to her physician, who ordered a series of blood tests. The blood work came back with abnormal results, leading to her muscle biopsy and referral to the metabolic clinic. Marie’s blood was subjected to the same metabolic panel used before with the following results:
Blood Metabolic Panel
Blood Glucose +
Glucose-6-phosphate ++
Fructose-6-phosphate ++
Fructose-1,6,bisphosphate -
Glyceraldehyde-3-phosphate -
1,3-bisphosphoglycerate -
Pyruvate -
ATP -
Red Blood Cell Concentration -

Marie’s muscle biopsy was also analyzed and showed an excess of glycogen.


Question 3:
What is the most likely enzyme deficiency for Marie?
A. Hexokinase
B. Phosphofructokinase
C. Triose Phosphate Isomerase
D. Pyruvate Kinase
E. Aldolase

Question 4:
If you wanted to test the ability of red blood cells to complete glycolysis what compound would you try to detect?
A. Fructose-6-phosphate
B. Aldolase
C. Pyruvate
D. Phosphofructokinase
E. Dihydroxyacetone phosphate


Question 5:
If you used a sample of Marie’s blood for this, what compound could you add to enable these cells to complete glycolysis?
A. Glucose
B. Fructose-1,6-bisphosphate
C. Insulin
D. Glucagon
E. Fructose-6-phosphate


Patient 3:
Leo is a 25-year-old accountant that is not anemic, has perfect teeth, but has experienced two fainting spells recently. One happened after accidentally drinking a non-diet soda; the other after eating “naturally sweetened” fruit salad. His dentist referred him to Dr. Saccharo’s clinic. Dr. Saccharo suspects Leo may have Hereditary Fructose Intolerance (HFI) and has recommended a closely monitored fructose tolerance test.

Hereditary Fructose Intolerance is a recessive disorder where individuals lack a functional copy of one isoform of the enzyme aldolase, specifically Aldolase B (also known as fructose-1-phosphate aldolase). In the liver, fructose is phosphorylated by Fructokinase to fructose-1-phosphate, then is cleaved by Aldolase B to glyceraldehyde and dihydroxyacetone phosphate. Fructose-1-phosphate is also a known allosteric inhibitor of Glycogen Phosphorylase, the primary enzyme responsible for releasing glucose from glycogen.

Question 6:
As compared to a normal individual that consumes fructose, a person with HFI who ingested fructose would have (select all that apply):
A. High levels of blood fructose
B. High levels of blood fructose-1-phosphate
C. High levels of blood glucose
D. Low levels of blood fructose
E. Low levels of blood glucose


That afternoon Leo undergoes the fructose tolerance test with the following results:

Question 7:
Based on the results of the test, what was the effect of giving Leo the intravenous fructose?
A. A rise in blood glucose levels
B. A decrease in blood glucose levels
C. An increase in glycogen stores
D. A rapid drop in blood pressure


However there were complications: Soon after the test Leo orders and drinks a cup of tea, but after half the cup Leo passes out. Dr. Saccharo orders two sequential blood glucose checks. The first was 50 mg/dl and 15 minutes later Leo’s blood glucose was down to 40 mg/dl. With those results Dr. Saccharo injected something into Leo’s IV and within minutes Leo was back to normal.

Question 8:
From these results does it appear that Leo has HFI?
A. Yes
B. No
C. It is unclear from the results


Question 9:
What did Dr. Saccharo inject into Leo’s IV line?
A. Insulin
B. Glucagon
C. Glucose
D. Fructose
E. Phosphofructokinase

Dr. Saccharo puts Leo on a restricted diet and orders follow-up visits.

Question 10:
Which of the following foods/ingredients would Leo NOT be allowed to eat?
A. Artificial sweeteners
B. High starch foods, such as potatoes
C. Sweet tea made with cane sugar
D. Any dairy products

Dr. Saccharo puts Leo on a restricted diet and orders follow-up visits.

Case Study Section 2 – glycolysis
Based on “Monday at the Metabolic Clinic, Adventures in Glycolysis” by Nancy Boury (National Center for Case Study Teaching in Science)

Background:
You have been chosen for a very competitive undergraduate clinical internship at St. Visintainer’s Hospital and Metabolic Clinic working with Dr. Saccharo, an expert in enzyme deficiency disorders related to glycolysis. Before your first day Dr. Saccharo has asked that you review the reactions of glycolysis and the concept of isoenzymes.

Recall that isoenzymes are groups of enzymes that catalyze the same reaction in that they use the same reactants to product the same products. They may have different genes, tissue expression, developmental timing of expression, and affinities for their substrates. As an example, phosphofructokinase-1 has 3 isoenzyme forms: PFK-L is expressed in the liver and the gene is found on chromosome 21; PFK-M is expressed in the muscle and the gene is found on chromosome 12; and PFK-P is expressed in platelets and the gene is found on chromosome 10.

Question 9:
What did Dr. Saccharo inject into Leo’s IV line?
A. Insulin
B. Glucagon
C. Glucose
D. Fructose
E. Phosphofructokinase

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