Chemistry Reference
In-Depth Information
(as illustrated in Chapter 5). For a simple reason, sequences of the carbohydrate
chains have been most intensely studied in pigs and to a somewhat lesser degree
in cattle [5]. In these two species, it is feasible to collect suffi cient amounts of ZP
glycoproteins. To give an idea on actual quantities, a single porcine ZP contains
about 30 ng of glycoproteins and a bovine ZP about 20 ng, while the total yield of
ZP glycoproteins per ovary is 10 times higher in pigs. Effi cient large- scale isolation
methods greatly facilitated the elucidation of glycan composition and structures
for porcine ZP glycoproteins. By gel electrophoresis, porcine ZP glycoproteins can
be resolved into two components, with molecular masses of about 55 and 90 kDa.
The 55-kDa component represents about 80% of the total glycoprotein content and
consists of ZP3 (ZPC) and ZP4 (ZPB), which can be separated only after partial
deglycosylation with endo-
-galactosidase. Each of the polypeptides has fi ve
sequons for
N
- glycosylation (positions of
N
-glycan sequons of the human ZP gly-
coproteins are shown for comparison in Figure 24.2). Carbohydrate composition
analysis of the glycoproteins detected the presence of four
N
- glycans and six
O
-glycans on ZP3 (ZPC) as well as three
N
- glycans and three
O
- glycans on ZP4
(ZPB). For further analysis, the
N
-linked glycans were released by hydrazinolysis
β
Figure 24.2
The modular architecture of the human ZP genes (aa = amino acids). Source:
UniProtKB/SwissProt.
