perturbation of protein conformation . myoglobin and hemoglobin

1. Muhammad Saeed
M.Phil Biochemistry

2.  The majority of protein molecules must fold into defined
three-dimensional structures to acquire functional activity.

3.  Metastable proteins tend to populate misfolded species that
are prone to forming toxic aggregates, including soluble
oligomers and fibrillar amyloid deposits, which are linked
with neurodegeneration in Alzheimer and Parkinson disease,
and many other pathologies

4.  To prevent or regulate protein aggregation, all cells contain an
extensive protein homeostasis (or proteostasis) network
comprising molecular chaperones and other factors.
 These defense systems tend to decline during aging,
facilitating the manifestation of aggregate deposition diseases

5.  Myoglobinuria
 Release of myoglobin from muscle cells in urine is called
Myoglobinuria.
 Following massive crush injury, myoglobin released from damaged
muscle fibers colors the urine dark red.
 Myoglobin can be detected in plasma following a myocardial infarction,
but assay of serum enzymes provides a more sensitive index of
myocardial injury.

6.  Any process that interferes with the storage or use of energy
by muscle cells can lead to myoglobinuria.
 The release of myoglobin from muscle cells is often
associated with an increase in levels of creatine kinase
(CK), aldoses, lactate dehydrogenase (LDH), serum
glutamic-pyruvic transaminase (SGPT), and other enzymes

8.  Thalassemia's
 The genetic defects known as thalassemia's result from the
partial or total absence of one or more α or β chains of
hemoglobin.
 Over 750 different mutations have been identified, but only
three are common.

9.  Certain mutant hemoglobin's are common in many
populations, and a patient may inherit more than one type.
 Hemoglobin disorders thus present a complex pattern of
clinical phenotypes.

11.  Glycated Hemoglobin (HbA1c)
 The term HbA1c refers to glycated haemoglobin.
 It develops when haemoglobin, a protein within red blood
cells that carries oxygen throughout your body, joins with
glucose in the blood, becoming ‘glycated’

12. When blood glucose enters the erythrocytes, it
glycates the ε-amino group of lysine residues and
the amino terminals of hemoglobin.

14.  Methemoglobinemia
 Methemoglobinemia is a blood disorder in which too little
oxygen is delivered to your cells.
 Oxygen is carried through your bloodstream by
hemoglobin, a protein that’s attached to your red blood
cells.

15.  However, there’s a specific type of hemoglobin known as
methemoglobin that carries oxygen through your blood but doesn’t
release it to the cells.
 If your body produces too much methemoglobin, it can begin to replace
your normal hemoglobin. This can lead to not enough oxygen getting to
your cells.

17.  By Evan M. Braunstein , MD, PhD, Johns Hopkins School of
MedicineLast full review/revision Mar 2019| Content last
modified Mar 2019
 https://www.healthline.com/health/methemoglobinemia
 Harper's Illustrated Biochemistry, 28th Edition (LANGE
Basic Science)