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
379
observed a progressive uptake of the isotope over a 24 h period; the
3 5
S 0 4
2 - being concentrated selectively in the perinuclear cytoplasm
of the fibroblasts. From the third hour onwards, as the intracellular
intake increased, an extracellular accumulation of sulphate was
observed in the neighbourhood of the cells and later in the intercellular spaces. Collagenase and elastase did not act on the uptake
of the radioactive isotope.
The interpretation of sulphate uptake in relation to acid mucopolysaccharide production in tissue cultures, however, is made a little
difficult by the suggestion of Grossfeld et al. (1957) that the sulphation
of acid mucopolysaccharide molecules might proceed independently
of synthesis and polymerization, and the data presented by Morris
(1960), which suggests that acid mucopolysaccharide production and
sulphate fixation proceed at different rates.
It is now clear that inorganic sulphate is not incorporated directly
into the acid mucopolysaccharide, but is transferred through the intermediary of 3-phosphoadenosine-5-phosphosulphate (PAS) (D'Abramo
and Lipmann, 1957; Robbins and Lipmann, 1957), the latter being
formed through the activity of the sulphate-activating enzymes,
ATP-sulphurylase and adenosine-5-phosphosulphatase (Robbins and
Lipmann, 1958; Wilson and Bandurski, 1958). A detailed consideration
of recent investigations, notably by Adams (1959a, b , 1960), Suzuki
and Strominger (1959, 1960a, b , c ) , Suzuki (1960) and Watkins and
Spencer (1961), on the nature of the primary sulphate-acceptors
is scarcely relevant to this review. In summary, such studies have
shown that sulphate can be incorporated directly into the acceptor
molecules without the simultaneous addition of monosaccharide units,
but it is yet uncertain whether incorporation occurs during the synthesis of the polysaccharide chain, or after the formation of the latter
is complete.
E. T U R N O V E R OF M U C O P O L Y S A C C H A R I D E S
A detailed study of the turnover of mucopolysaccharides in the skin
of rabbits and rats injected with either
1 4
C-acetate and N a 2
3 5
S 0 4
or
1 4
C-glucose and N a 2
3 5
S 0 4 has been made by Dorfman and his
collaborators (reviewed by Dorfman and Schiller, 1958). The use of the
three labelled precursors enabled the turnover of the whole mucopolysaccharide molecule to be studied; acetate was incorporated
solely into the acetyl groups of the mucopolysaccharide, and was not
used for the resynthesis of hexose and hexosamines. The results obtained
established unequivocally that in both tissues (a) all components of
a given mucopolysaccharide turnover at the same rate and (b)
379
observed a progressive uptake of the isotope over a 24 h period; the
3 5
S 0 4
2 - being concentrated selectively in the perinuclear cytoplasm
of the fibroblasts. From the third hour onwards, as the intracellular
intake increased, an extracellular accumulation of sulphate was
observed in the neighbourhood of the cells and later in the intercellular spaces. Collagenase and elastase did not act on the uptake
of the radioactive isotope.
The interpretation of sulphate uptake in relation to acid mucopolysaccharide production in tissue cultures, however, is made a little
difficult by the suggestion of Grossfeld et al. (1957) that the sulphation
of acid mucopolysaccharide molecules might proceed independently
of synthesis and polymerization, and the data presented by Morris
(1960), which suggests that acid mucopolysaccharide production and
sulphate fixation proceed at different rates.
It is now clear that inorganic sulphate is not incorporated directly
into the acid mucopolysaccharide, but is transferred through the intermediary of 3-phosphoadenosine-5-phosphosulphate (PAS) (D'Abramo
and Lipmann, 1957; Robbins and Lipmann, 1957), the latter being
formed through the activity of the sulphate-activating enzymes,
ATP-sulphurylase and adenosine-5-phosphosulphatase (Robbins and
Lipmann, 1958; Wilson and Bandurski, 1958). A detailed consideration
of recent investigations, notably by Adams (1959a, b , 1960), Suzuki
and Strominger (1959, 1960a, b , c ) , Suzuki (1960) and Watkins and
Spencer (1961), on the nature of the primary sulphate-acceptors
is scarcely relevant to this review. In summary, such studies have
shown that sulphate can be incorporated directly into the acceptor
molecules without the simultaneous addition of monosaccharide units,
but it is yet uncertain whether incorporation occurs during the synthesis of the polysaccharide chain, or after the formation of the latter
is complete.
E. T U R N O V E R OF M U C O P O L Y S A C C H A R I D E S
A detailed study of the turnover of mucopolysaccharides in the skin
of rabbits and rats injected with either
1 4
C-acetate and N a 2
3 5
S 0 4
or
1 4
C-glucose and N a 2
3 5
S 0 4 has been made by Dorfman and his
collaborators (reviewed by Dorfman and Schiller, 1958). The use of the
three labelled precursors enabled the turnover of the whole mucopolysaccharide molecule to be studied; acetate was incorporated
solely into the acetyl groups of the mucopolysaccharide, and was not
used for the resynthesis of hexose and hexosamines. The results obtained
established unequivocally that in both tissues (a) all components of
a given mucopolysaccharide turnover at the same rate and (b)