Table 1. Hydrolysis of fluorogenic substrates by longipain.

Substratea	K m (µM)	k cat (s−1)	k cat/K m (µM−1 s−1)
Z-Arg-Arg-MCA (substrate for cathepsin B)	16.0±0.2	8.0×102	50
Z-Phe-Arg-MCA (substrate for cathepsin B/L)	12.1±0.08	5.5×102	45
Suc-Leu-Leu-Val-Tyr-MCA (substrate for chymotrypsin)	NHb

^aFive micrograms of longipain (5 µg) were included in the standard reaction mixture containing 25 mM citric acid/sodium phosphate, pH 6.0, 5 mM DTT, 0.4 mM substrate in a final volume of 100 µl. The hydrolytic activity was monitored by spectrofluorometry at 360 nm for excitation and 465 nm for emission.

^bNH, not hydrolysed.