Biochemistry at the movies: Lorenzo’s Oil


Below, the scene that shows Lorenzo’s father finding out that his 5 year-old son has got Adrenoleukodistrophy (ALD),  and faces a slow, painful death…   

For more information about this movie go to the Biochemistry at the Movies page

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A Nutritional Deficiency (N-01)


A 10 month infant, son of an adolescent mother, presents with painful swelling in long bones, sunken sternum, purpura (hemorrhagic lesions in the skin) and gum lesions around the four teeth that have already erupted. During the interview, the mother tells you that the infant diet is based on milk only, because she has heard it is better that infants do not eat anything else but milk until they are one year old, so not fruit juice or vegetables are consumed by the baby. She says she exposed the infant to the sun light for 15 minutes every day. With this information, we already suspect that the infant has:

a) Vitamin D deficiency

b) Vitamin C deficiency

 

c) Vitamin K deficiency

d) Ca deficiency

e) Phospate deficiency

 

Answer

Answer to N-01


Answer: (b) Vitamin C deficiency

 

                                                                          

Vitamin C structure

 Vitamin C (aka Ascorbic acid)

Vitamin C biological functions include:

a)      Cofactor of specific hydroxylation reactions in important processes as the synthesis of collagen, catecholamines, and serotonin.

b)      Facilitation of iron absorption

c)      Anti-oxidant

Sources of Vitamin C:

The richest sources are fruits and vegetables. Common rich sources are citrus fruits and their juices.                                                                      

 

 

oranges

Meats, notably liver, contains vitamin C; however they are not a reliable source for daily requirements. Pressure cooking, roasting, frying, grilling, and other overheating procedures decompose vitamin C. Another way of wasting Vitamin C contents in some foods is the lost of this vitamin when it dissolves in boiling water that is not consumed later.

Scurvy

The deficit of vitamin C produces Scurvy, characterized by superficial hemorrhages, and wounding healing delays. Inflammation and bleeding of the gums with loss of teeth are characteristics of this disease.

                                                                    

 

 

Hemorrhagic “dots” (petechias) appears in the skin around hair follicles. The hemorrhagic lesions increase in size and become more extended with time if the condition is not cured.

The patient shows low resistance to infections and delayed tissue regeneration, so any wound can be infected.

The pathobiochemistry of this disease is related to the participation of Vitamin C in the biosynthesis of collagen. Collagen is the most abundant protein in the human body. Collagen forms molecular cables that strengthen the tendons, and a mesh-like net that support the skin and internal organs. Bones and teeth are made by the addition of minerals to collagen. Typical manifestations of impaired synthesis of collagen as a consequence of a deficit of vitamin C appear in those tissues rich in collagen such as skin, bones, cartilage, dentine,  and capillary walls of blood system.  Hydroxyproline and hydroxylysine are particularly important in the structure of collagen.These modified amino acids give stability to the collagen molecule, and act as attachment site for structural carbohydrates. These amino acids are hydroxylated in the endoplasmic reticulum as a result of posttranslational modifications (the proline and the lysine that are already part of the precursor chain are converted to the corresponding hydroxylated amino acids).

Vitamin C deficiency slows the production of hydroxyproline and hydroxylysine and consequently the construction of new collagen, ultimately causing scurvy. Most of the cases of infant scurvy occur before 24 months of age. Usually, they are consequence of a deficient diet caused by lack of resources and/or lack of appropriate information. The prolonged consumption of pasteurized or overheated milk and the deficient ingestion of citrics and other fruits and vegetables, are risk factors.  

Recommended reading for additional information about Scurvy:

Kumaravel Rajakumar: Scurvy

Editors: Kathryn Schwarzenberger, MD; Michael J Wells, MD; Van Perry, MD,; Catherine Quirk, MD; Dirk M Elston, MD: Scurvy

Food Sources of Vitamin C ranked by milligrams of vitamin C per standard amount; also calories in the standard amount. (All provide ≥ 20% of RDA for adult men, which are 90 mg/day.)

Food, Standard Amount Vitamin C (mg) Calories
Guava, raw, ½ cup 188 56
Red sweet pepper, raw, ½cup 142 20
Red sweet pepper, cooked, ½ cup   116 19
Kiwi fruit, 1 medium 70 46
Orange, raw, 1 medium 70 62
Orange juice, ¾ cup 61-93 79-84
Green pepper, sweet, raw, ½ cup 60   15
Green pepper, sweet, cooked, ½ cup 51   19
Grapefruit juice, ¾ cup 50-70 71-86
Vegetable juice cocktail, ¾ cup 50 34
Strawberries, raw, ½ cup 49 27
Brussels sprouts, cooked, ½ cup 48 28
Cantaloupe, ¼ medium 47 51
Papaya, raw, ¼ medium 47 30
Kohlrabi, cooked, ½ cup 45 24
Broccoli, raw, ½ cup 39 15
Edible pod peas, cooked, ½ cup 38 34
Broccoli, cooked, ½ cup 37 26
Sweetpotato, canned, ½ cup 34   116
Tomato juice, ¾ cup 33 31
Cauliflower, cooked, ½ cup 28 17
Pineapple, raw, ½ cup 28 37
Kale, cooked, ½ cup 27 18
Mango, ½ cup 23 54

Source: Nutrient values from Agricultural Research Service (ARS) Nutrient Database for Standard Reference, Release 17. Foods are from ARS single nutrient reports, sorted in descending order by nutrient content in terms of common household measures. Food items and weights in the single nutrient reports are adapted from those in 2002 revision of USDA Home and Garden Bulletin No. 72, Nutritive Value of Foods. Mixed dishes and multiple preparations of the same food item have been omitted from this table.

A newborn with Maple Syrup Disease (P-01)


Five days after birth an infant becomes irritable, lethargic and difficult to feed. Two days later, the neonate presents seizures and consequently the parents look for professional help immediately. The patient is hospitalized and physical examination shows an opisthotonic posture and rigidity of the arms. During the interview, the mother mentions a strange odor, like burned sugar, in “wet diapers” that were not disposed immediately. The pediatrician then consider the possibility of this patient having Maple Syrup Urine Disease and looks for (and finds) the characteristic odor in the cerumen of the infant.  Laboratory tests are done immediately and the results show a marked ketonuria, and hyponatremia. A study of plasma amino acids reveals an increase of leucine, valine and isoleucine in plasma, typical of MSUD, since this disease is a consequence of the lack of an enzyme that participates in the degradation of these:

 

a)      polar amino acids

b)      branched chain amino acids

c)      aromatic amino acids

d)     sulfurated amino acids

e)      acid amino acids

f)       basic amino acids

 

 

Answer

 

Related post

 

 

Answer to P-01


 

Original Question P-01

 

Answer: (b)

 

 Explanation: Amino acids are different because they differ in the kind or the lateral chain ( R) that they have,

                                General Formula of amino acids

so the characteristics of these lateral chains have been used for classify them.   

 

Very used classifications are the following:

 

Classification according to the side chain polarity

 

 Nonpolar neutral (Hydrophobic): Glycine, Alanine, Valine, Leucine, Isoleucine, Proline, Methionine, Phenylalanine

Polar neutral: Serine, Threonine, Cysteine, Asparagine, Glutamine, Tyrosine, Tryptophan

Polar acidic (AKA Negatively charged amino acids, AKA acid amino acids): Aspartate, Glutamate

Polar basic (AKA positively charged amino acids, AKA basic amino acids): Lysine, Arginine, Histidine 

 

 

Other classifications consider also different subgroups, or even can include amino acids of different groups, based in other common chemical characteristics. Examples of these amino acid subgroups are:

          Aromatic amino : Tyrosine, Tryptophan, phenylalanine

          Amino acids containing Sulfur: Cysteine and Methionine 

         Amino acids with Hydroxyl group: Serine, Threonine, Tyrosine 

         Branched chain amino acids: Valine, Leucine, Isoleucine 

 

The best way to be able to classify an amino acid is by knowing the chemical structure. If the structure is known, it is possible to answer any question related to amino acid classification. I strongly recommend studying the individual amino acid structure of protein amino acids, in order to be able to understand the influence of mutations in the functionality and electrophoretic behavior of proteins, as we will see in next weeks.