SECTION 10.4
Serum Glycoproteins
169
Blood Group (abbreviation)
Locus Name
Protein
TABLE 10-6
Functions of Blood Group Protein Antigens of Erythrocytes
a. Proteins that contribute to the structural integrity
Rhesus (Rh)
Gerbich (Ge)
Diego (Di), Wright (Wr)
XK
b. Proteins with complement-related functions
Cromer (Cr)
c. Proteins with receptor functions
Duffy (Fy)
d. Proteins with transport functions
Diego (Di), Wright (Wr)
Kidd (Jk)
Colton (Co)
e. Proteins with enzymatic activity
Kell (K,k,Kp,Js)
Cartwright (Yt)
RH
Rh acylproteins
GYPC
Glycophorins C and D
AE1
Anion channel protein
Kx
Kx protein
DAF
Decay accelerating factor (CD55)
Fy
Chemokine receptor
AE1
Anion channel protein
JK
Urea transporter
AQP1
Aquaporin 1 water channel protein
KEL
93kD protein, metalloproteinase (?)
YT
Acetylcholinesterase
asialoglycoproteins, are taken up after binding to receptors
on hepatocytes. The bound asialoglycoprotein is internal-
ized by a process known as
receptor-mediated endocytosis
(Chapter 11) and subjected to lysosomal degradation. In
TABLE 10-7
Blood Group Protein Antigens as Microbial Receptors*
Oligosaccharides
P
E scherichia coli,
Parvovirus B19
Lewis (Leb)
H elico b a cter p y lo ri
H, A
C an dida albican s
Proteins
Glycophorin A (MN)
Plasmodium falciparum
Decay accelerating factor
Echovirus,
E. coli
(Cromer)
CD44 (Indian)
Poliovirus
Duffy
P lasm odiu m vivax,
P lasm odiu m kn ew lesi
AnWj
H. influenzae
*Modified and reproduced with permission from M. J. Telen.
Erythrocyte Blood Group Antigens: Polymorphisms of functionally
Important Molecules. Seminars in Hematology 33, 302 (1996).
liver disease, the plasma levels of asialoglycoproteins are
elevated.
The internalized glycoproteins are catabolized to their
monomeric units by the lysosomal enzymes. The oligosac-
charides are degraded sequentially by specified hydro-
lases, starting from the nonreducing termini. Hereditary
deficiency of some of these enzymes has been reported:
a-D-mannosidase in mannosidosis, a-L-fucosidase in
fucosidosis,
glycoprotein-specific
a-neuraminidase in
sialidosis, and aspartylglycosaminidase in aspartylgly-
cosaminuria. In these disorders, undigested or partially
digested oligosaccharides derived from glycoproteins
accumulate within the lysosomes. Keratin sulfate (a gly-
cosaminoglycan, Chapter 11) also accumulates, presum-
ably because the above enzymes are required for its
degradation.
These
disorders
are
inherited
as
auto-
somal recessive traits and can be diagnosed prena-
tally.
Clinically,
they
resemble
mild forms of mu-
copolysaccharidosis (Chapter 11). There is no definitive
treatment.
Removal of senescent red blood cells from the circula-
tion has been attributed to desialylation of the membrane
glycoproteins.
In vitro
removal of sialic acid from hu-
man red blood cells and introduction of the modified cells
into the circulatory system result in drastic shortening of
their life span. However, aging and removal of red blood
