Cholesteryl esters with various chain lengths of
fatty acid, radioactive (C2-C18:1) and fluorescent (
pyrene butanoic and
decanoic acid, P4 and P10, respectively) were synthesized and their hydrolysis was investigated in lymphoid cell lines from normal subjects and from
Wolman's disease patients. The comparison of their hydrolysis showed that three
cholesterol esterases were present in normal lymphoid cell lines: the first, active at pH 4.0, hydrolysed preferentially
cholesteryl esters of acyl chain length more than 8 carbons, and P10-cholesteryl
ester. This
acid cholesterol esterase, strongly inhibited by SH-blocking agents and resistant to
E600, was severely deficient in Wolman lymphoid cell lines and corresponded to
acid lysosomal
lipase. The second and the third
cholesterol esterases, active at pH 6.0 and 8.0, respectively, hydrolysed shorter-chain derivatives: the pH 8.0
enzyme was specific for short-chain derivatives (
cholesteryl acetate,
butyrate and P4), whereas the pH 6.0 activity showed a broader specificity, since it hydrolysed all the
cholesteryl esters, with a maximum of activity on
cholesteryl acetate and
butyrate. The pH 6.0 and 8.0
enzymes were heat-labile, inhibited by
E600, resistant to SH-blocking agents and not deficient in Wolman lymphoid cell lines. The hypothetical physiological role of these
enzymes is discussed.