Chemistry Reference
In-Depth Information
Info Box 2
Orthologs and paralogs are two types of homologous sequences, homologs.
Orthologs are genes in different species that evolved from a common ancestral
gene by speciation. Usually, orthologs retain the same function. Paralogs are
homologous genes within a single species that diverged by gene duplication.
upper-level element emerges from interactions between elements at the immedi-
ately lower level via nonlinear and large-scale interactions, called self-organization.
It is not easy to elucidate the whole mechanism of pathogenesis, even if disruption
of a gene function displays some abnormal phenotype at the higher level of organ-
ism formation. To comprehend the biological processes, we cannot skip the inter-
mediate levels. The same is true for the study of human diseases.
Information on individual gene KO mice is available in the Mouse Genome
Informatics (MGI) database of the Jackson Laboratory (http://www.informatics.
jax.org/ ).
23.2
Specifi c Features of Glycogene KO
23.2.1
Relationship between Glycogenes and Related Glycans
Glycans represent the secondary gene products formed by the reactions of glycan-
synthesizing enzymes. The biosynthesis of glycans is regulated by the activity of
the glycan-synthesizing enzymes, their substrate specifi city and their localization
in specifi c tissue sites. Genes that encode the glycan- synthesizing enzymes, includ-
ing glycosyltransferases, sulfotransferases, nucleotide- sugar transporters and
related enzymes, are called ' glycogenes ' (please see Chapters 6 - 11 for activity
profi les of these enzymes). More than 180 glycogenes have been cloned at present.
Information on individual glycogenes is available in the GGDB GlycoGene Data-
Base of the National Institute of Advanced Industrial Science and Technology,
Japan (http://riodb.ibase.aist.go.jp/rcmg/ggdb/). This database also links to the
MGI database.
Since carbohydrate chains are basic components of organisms, they are thought
to function in a wide variety of biological processes. In fact, the inactivation of
specifi c glycogenes in KO mice has proved that glycogenes are essential for devel-
opment, the immune system, the nervous system, the reproductive system, cancer
progression, the establishment of infection, and so on (Table 23.1 ) [1 - 4] ; however,
the actual functions of most of the carbohydrate chains in the glycoconjugates
remain unknown (for human diseases of glycosylation, please see Table 22.1 ;
please see also Table 27.4 ).
