chapter 11
Heteropolysaccharides II: Proteoglycans and Peptidoglycans
FIGURE 11-10
Formation and function of lysosomes. Lysosomal enzymes are synthesized in the rough endoplasmic reticulum. Those
with appropriate recognition markers are processed and packaged into primary lysosomes in the complex network of the
Golgi apparatus. 1, 2, and 3 represent digestion of extracellular substance segregated into a heterophagosome; 1,4, and
5, digestion of segregated cytoplasmic material (autophagosome); 1
, extrusion of lysosomal enzymes that will act
extracellularly (e.g., collagenase); and 7, a residual body. [Reproduced with permission from L. C. Junqueira, J. Carneiro,
and J. L. Long,
B a sic H isto lo g y,
5th ed. Appleton & Lange, Norwalk, CT, 1986. ©1986 Appleton-Century-Crofts.]
cornea. Types IH, II, III, and VIII are characterized by
severe mental retardation, while types IS, IV, and VI
exhibit normal intelligence. Patients with different en-
zyme deficiencies may exhibit phenotypic similarities
(pleiotropism), and they may also exhibit variation in
clinical severity with the same enzyme deficiency (al-
lelic variants). The enzyme deficiency can be estab-
lished by assays on peripheral lymphocytes or cultured
fibroblasts. Prenatal diagnosis is possible but requires
successful culture of amniotic fluid cells and assay of
specific enzymes. No specific therapy is available. Man-
agement focuses on providing prognostic information and
11.2 Peptidoglycans
Peptidoglycans are components of bacterial cell walls
and consist of heteropolysaccharide chains cross-linked
by short peptide chains. These cell walls bear the anti-
genic determinants; when exposed to them, humans (and
other mammalian species) develop specific antibodies to
defend against bacteria. Bacterial virulence is also related
to substances associated with the cell wall. Cell wall syn-
thesis is the target for the action of the penicillins and
Bacterial cell walls are rigid and complex, enable the
cells to withstand severe osmotic shock, and survive in a
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