1 1 . M U C O P O L Y S A C C H A R I D E S IN T I S S U E C U L T U R E
355
and mucoprotein are reserved for conjugates ofthe mucopolysaccharides
with peptides and proteins respectively. Thus, all combinations of the
mucopolysaccharides and proteins are defined as mucoproteins, no
distinction being made, as in other classifications, between mucoproteins and glycoproteins, with regard to the nature o f the linkage
between the components (ionic (?) and covalent). The term glycoprotein is reserved for proteins that contain (neutral) polysaccharides,
frequently of low molecular weight, as minor components or prosthetic
groups, and is given the prefix "sialo-" when the carbohydrate
entity contains sialic acid. Although this terminology has limitations,
it is adequate for present purposes and also circumvents the problems
that are raised by recent work indicating that a sialoglycoprotein may
be the "protein" component of a mucoprotein (Anderson, 1962).
The terms mucin and mucus are used purely descriptively to refer to
native secretions, presumably mixtures of mucoproteins.
B. C O M P O S I T I O N A N D D I S T R I B U T I O N OF
M U C O P O L Y S A C C H A R I D E S
What little work has been done on mucopolysaccharide synthesis
and metabolism in tissue culture has been concerned mostly with
acid mucopolysaccharides. The composition, some physical properties,
principal tissues of origin and some examples of the production of
these substances in Tissue Culture are summarized in Table I. The
polysaccharides listed in the Table fall into two groups: the nonsulphated and the sulphated mucopolysaccharides. The sulphated
mucopolysaccharides are characteristic components of the extracellular ground substance of connective tissue, and occur generally, if
not invariably, in association with protein or proteins. The nonsulphated mucopolysaccharides also occur in structural elements, but,
in addition, are found in tissue fluids.
It appears possible that at least certain of the mucopolysaccharides
may be combined covalently with one protein (Partridge and Elsden,
1961a) and this mucoprotein then linked by ionic forces with another.
In cartilage a number of chondroitin sulphate-A (CSA-A) chains
seem to be bound to a protein (Partridge, Davis and Adair, 1961) or
sialoglycoprotein (Anderson, 1960, 1961, 1962) core to form a macromolecular complex of which the minimum molecular weight is about
4 x l 0
6 (Partridge et al., 1961). This and similar (acid) mucoproteins
behave as highly negatively charged polyelectrolytes by virtue of both
the presence of carboxyl and sulphate groups in the carbohydrate
chain. Such molecules interact strongly with cations, and in doing
so undergo changes in structure. Thus, in the absence of ions the
355
and mucoprotein are reserved for conjugates ofthe mucopolysaccharides
with peptides and proteins respectively. Thus, all combinations of the
mucopolysaccharides and proteins are defined as mucoproteins, no
distinction being made, as in other classifications, between mucoproteins and glycoproteins, with regard to the nature o f the linkage
between the components (ionic (?) and covalent). The term glycoprotein is reserved for proteins that contain (neutral) polysaccharides,
frequently of low molecular weight, as minor components or prosthetic
groups, and is given the prefix "sialo-" when the carbohydrate
entity contains sialic acid. Although this terminology has limitations,
it is adequate for present purposes and also circumvents the problems
that are raised by recent work indicating that a sialoglycoprotein may
be the "protein" component of a mucoprotein (Anderson, 1962).
The terms mucin and mucus are used purely descriptively to refer to
native secretions, presumably mixtures of mucoproteins.
B. C O M P O S I T I O N A N D D I S T R I B U T I O N OF
M U C O P O L Y S A C C H A R I D E S
What little work has been done on mucopolysaccharide synthesis
and metabolism in tissue culture has been concerned mostly with
acid mucopolysaccharides. The composition, some physical properties,
principal tissues of origin and some examples of the production of
these substances in Tissue Culture are summarized in Table I. The
polysaccharides listed in the Table fall into two groups: the nonsulphated and the sulphated mucopolysaccharides. The sulphated
mucopolysaccharides are characteristic components of the extracellular ground substance of connective tissue, and occur generally, if
not invariably, in association with protein or proteins. The nonsulphated mucopolysaccharides also occur in structural elements, but,
in addition, are found in tissue fluids.
It appears possible that at least certain of the mucopolysaccharides
may be combined covalently with one protein (Partridge and Elsden,
1961a) and this mucoprotein then linked by ionic forces with another.
In cartilage a number of chondroitin sulphate-A (CSA-A) chains
seem to be bound to a protein (Partridge, Davis and Adair, 1961) or
sialoglycoprotein (Anderson, 1960, 1961, 1962) core to form a macromolecular complex of which the minimum molecular weight is about
4 x l 0
6 (Partridge et al., 1961). This and similar (acid) mucoproteins
behave as highly negatively charged polyelectrolytes by virtue of both
the presence of carboxyl and sulphate groups in the carbohydrate
chain. Such molecules interact strongly with cations, and in doing
so undergo changes in structure. Thus, in the absence of ions the