Chemistry Reference
In-Depth Information
Figure 11.3
Subsequent enzymatic steps during the lysosomal degradation of a HS chain.
GAG-degrading enzymes are also secreted from many prokaryotes (that is
Arthrobacter aurescens
,
Flavobacterium heparinum
). These enzymes (chondroitinase
ABC, several forms of heparitinase and heparinase) are important tools for
the structure elucidation of GAG. They cleave glycosidic bonds by removing
a water molecule (lyases) forming an unsaturated uronate residue, while the
mammalian enzymes are hydrolases cleaving the glycosidic bonds by the addition
of water.
11.2
PG s
Basic data about PGs are given in Table 11.1. They are listed according to their
location to multicellular organisms. PGs are highly conserved in evolution and are
found from lower animals (
Drosophila melanogaster
,
Caenorhabditis elegans
,
Xenopus
laevis
) up to mammals and humans. The main functions of PGs are summarized
in Table 11.2 [2, 3] .
11.3
Large Aggregating (Hyaluronan- Binding) PG s
The large aggregating PGs aggrecan ( ACAN ), versican ( VCAN ), neurocan ( NCAN )
and brevican (BCAN) exist as extracellular PG aggregates [4-8]. Each aggregate is
composed of a central fi lament of hyaluronan (HA) with a various number of HA-
binding PGs. The interaction of HA and PGs (ACAN, VCAN, NCAN, BCAN) is
stabilized by the presence of a link protein (for its function as lectin, please see
Chapter 19 and the upper right part of Figure 19.1 ).
