J.'.~"";i'

Review ofLiterature
carbohydrate content and having a similar amino acid sequence to
plasminogen, and is attached by a disulfide bond to the apoBl00. It is
synthesized in the liver with a poor clearance from plasma it has 11
phenotypes and 19 genotypes (Howard and pizzo, 1993).
Lp (a) is carried in plasma on a protein carrier apolipoprotein (a)
which was found to have a 90% structural homology to plasminogen.
Inheritance of apolipoprotein (a) is controlled by a specific gene on
chromosome No.6 (Wang et al., 1994).
Lipoprotein(a) LP(a) is a distinct class oflipoprotein (as shown in
table 3) that is structurally related to LDL, because both lipoprotein
classes possess one molecule ofapo B-100 per particle and have similar
lipid compositions.(Durington,1995 & Marcovina, ,1995) However
unlike LDL, Lp(a) contains a carbohydrate-rich protein apo(a) that is
covalently bound to the apo B-lOO through a disulfide linkage. The
available evidence suggest that Lp(a) contains one molecule ofapo(a) and
one molecule of apo B-IOO per Lp(a) particle (Albers, et al. 1996).
Apo(a) is the unique protein componant of Lp(a) and exhibits a
significant sequence homology with plasminogen and a high degree of
variation in polypeptide chain length. Apo(a) is composed ofa serine
protease domain and a kringle-containing domain unlike plasminogen,
however, Lp(a) is not activated to form an active protease. The kringle
that is contiguous with the protease domain, kringle 5, shares 85% amino
acid homology with plasminogen kringle 5, whereas the kringle 4 domain
has 78 to 88% amino acid homology with kringle 4 ofplasminogen.
Apo(a) contains 10 distinct classes ofkringle 4-1ike domains that differ
from each other in amino acid sequence. Kringle 4 type I and kringle 4
types3 to 10 are present as a single copy on apo(a) particles. In contrast,
kringle 4 type 2 is present in variable number ofrepeats (3 to> 40) and
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