Specialization Of Proteins I (Foundations Exam 1)

Front 1

coenzymes

Back 1

special reactant for enzyme, essential for activity,derived from vitamins, may attach and detach from enzyme

Front 2

prosthetic groups

Back 2

organic, covalently attached to enzyme

Front 3

isozymes

Back 3

- two different enzymes that catalyze same reaction
- may utilize the same substrate

Front 4

nonfunctional plasma enzymes

Back 4

- appear in blood but have no physiological function in blood
- if found in blood, then indicative of cellular damage
example: AST/ALT/glutamyl transferase in blood means liver damage
- if mitochondrial enzymes are found in blood, indicative of severe cell injury and death

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allosteric regulation

Back 5

- effector molecule binds to enzyme at a site different from substrate
- changes conformation
- affects ability of enzyme to bind to substrate
example: hemoglobin

Front 6

enzyme regulation

Back 6

- substrate concentration
- cofactors
- isozymes
- allosteric regulation

Front 7

Kcat

Back 7

catalytic constant
- the efficiency of an enzyme to catalyze a reaction

Front 8

Km

Back 8

michaelis constant
- concentration of substrate required for 1/2 of the enzymes to be substrate bound and 1/2 Vmax
- an enzyme could have different Km's for different substrates

Front 9

collagen

Back 9

- most abundant structural protein in the body
- made in fibroblast (chondrocytes)
- alpha chain form into a tight triple helix

Front 10

triple helix

Back 10

- three pro-collagen (alpha) chains wound together
- 3.0 residues per turn
- rich in proline (smallest amino acid)
- glycine at every 3rd position
[Gly - X - Y]
- X is usually proline
- Y is usually lysine
- disulfide bonds: cross links between cysteines

Front 11

Collagen Type I

Back 11

- most abundant collagen in the body; present in scar tissue
- found in skin, tendon, arterial walls, bone (fibroblasts)

Front 12

Collagen Type II

Back 12

- hyaline cartilage, 50% of all cartilage protein
- cartilage, vitreous humor (chondrocytes)

Front 13

Collagen Type III

Back 13

- collagen of granulation tissue; produced quickly by young fibroblasts before tougher type I collagen is synthesized
- skin, muscle, frequently found with type I collagen (quiescent hepatocytes epithelial; fibroblasts)

Front 14

Collagen Type IV

Back 14

- part of filtration system in capillaries and glomeruli of kidney nephron
- all basal lamina (epithelial cells, endothelial cells, regenerating hepatocytes)

Front 15

osteogenesis imperfect (OI)

Back 15

"brittle bone disease"
- mutations primarily in the COL 1A1 and COL 1A2 genes
- encode the pro-alpha-1(I) and pro-alpha-2(I) chains
-affects type I collagen
-skin, tendons, arterial walls, bones
-protein is misfolded, then degraded
- significantly decreases the amount of collagen
- hyperelasticity of skin
- lack of strength and stiffness
- hearing loss, bone defects, muscle weakness, short stature, immobility

Front 16

Scurvy

Back 16

- vitamin C deficiency
- reduces hydroxylation of proline and lysine
- abnormal collagen trimer formation and cross-linking are abnormal
- weakened blood vessels and bleeding gums

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Ehlers-Danlos Syndrome (EDS) Type V

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- deficiency of lysyl oxidase
- inability to form stable crosslinks
- sx: thin skin and cardiac valves, hernias

Front 18

EDS Type VI

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- deficiency of lysyl hydroxyls
- lack of OH-Lys formation
- diminished cross-linking and immature fibers
- sx: hyperextensible joints, eye defects

Front 19

EDS Type VIIB

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- cleavage of N-terminal extensions is incomplete
- hip dislocations

Front 20

collagen turnover

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- dramatic degradation and re-synthesis of collagen fibrils during embryonic development
- in adults, half-lives of many weeks or months
- in bone, continually degraded and resynthesized as remodeling occurs
- example: high collagen turnover may be a sign of cancer

Front 21

degradation of collagen

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- initiated by cleavage of molecule at specific sites by collagenases
- after collagen unfolds, further degraded by gelatinizes and stromelysin
- increase in excretion in urine of hydroxyproline and hydroxylysine

Front 22

advanced glycosylation end products (AGE)

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- non-enzymatic glycosylation of collagen --> reversible short term
- AGE forms in long term high levels of sugar --> irreversible
- cross linking of lysine is permanent
- long half life allows for many cross links to occur
- prevents collagen turnover
**complications of diabetes
- cardiovascular disease
due to stiffer collagen --> stiffer vessels

Front 23

purpose of hydroxylation of proline

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- important role: aligning (assembling) the individual monomers in the proper register (alignment) of a tight helix required to form a triple helix

Front 24

defect in hydroxylation of proline

Back 24

if OH-Pro is not formed, the monomers fail to assemble into mature trimers and unprocessed collagens accumulate in the RER

Front 25

purpose of hydroxylation of lysine

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- essential for the subsequent glycosylation of the molecule by enzymatic attachment of sugars
- amount of OH-Lys and sugar content is determined by length of time in RER lumen

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consequences of increased glycosylation

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- hydroxyl groups on the sugars become hydrated
- lose its tensile strength
- babies have less tensile strength (more flexible) than adults due to more time spent in RER and more glycosylation

Front 27

purpose of glycosylation

Back 27

- aid in secretion to extracellular matrix and organization of fibrils

Front 28

consequences of defect in OH-Lys

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- diminished substrate for lysyl oxidase
-cross-link formation is markedly diminished
- collagen fibers fail to mature properly