Inhibition of rat liver cathepsins B and L by the peptide aldehyde benzyloxycarbonyl-leucyl-leucyl-leucinal and its analogues

Figures & data

Figure 1.  Synthetic procedures of ZLLLal and Its analogues. Synthetic procedures of Lsc(TosOH) (a), ZLLLal (b) and FuLLLal (c) are schematically shown. DIBAL, diisobutylaluminum hydride; Pd/C, activated palladium/charcoal; N₂H₄ H₂O, hydrazine hydrate; HOBt, 1-hydroxybenzotriazole; DCC, dicyclohexylcarbodiimide.

Table I.  Structures of ZLLLal and its analogues synthesized in this study.

	Inhibitor^*	Structure^†
a	ZLLLal
b	FuLLLal
c	NiLLLal
d	isoNiLLLal
e	MoSuLLLal
f	ZPLLal
g	ZPLLLal
h	AcPLLLal
i	APPLLLal
j	AcPPLLLal
k	ZLLLsc
l	ZPLLsc

* Inhibitors a, b and k are identical with compounds (7), (11) and (6), respectively, described in the text. ^† All the amino acid residues are in the L-form. Leu^*: Leu residue which has a hydrogen atom, but no oxygen atom on the carbonyl carbon (i.e. –CH = NNHCONH₂).

Table II.  Physico-chemical properties of ZLLLal and its analogues.

	Inhibitor	MS (m/z)	Mp (dec.) (°C)	[α]D (°) (c(%), MeOH)	Rf value^*	Retention time (min)^†
a	ZLLLal	475	80–84	− 63.9 (1.13)	0.76	37.1
b	FuLLLal	435	108–114	− 55.5 (0.94)	0.72	20.1
c	NiLLLal	446	144–150	− 66.7 (0.87)	0.74	19.3
d	isoNiLLLal	446	143–147	nd	0.68	21.9
e	MoSuLLLal	510	109–116	nd	0.68	11.7
f	ZPLLal	459	55–65	− 85.4 (0.93)	0.64	27.1
g	ZPLLLal	572	150–155	− 127.3 (0.94)	0.83	36.9
h	AcPLLLal	480	95–102	− 84.5 (0.81)	0.65	12.7
i	ZPPLLLal	669	78–84	− 151.8 (0.88)	0.75	36.3
j	AcPPLLLal	577	80–88	− 174.2 (0.92)	0.77	14.5
k	ZLLLsc	532	110–117	− 58.6 (1.02)	0.60	31.7
l	ZPLLsc	516	105–110	− 88.3 (0.98)	0.53	26.8

* The Rf values were obtained by TLC using CH₃Cl:MeOH (5:1 by vol.) as a solvent. ^† Retention time on HPLC. nd, not determined.

Figure 2.  Inhibition of rat liver cathepsin B by ZLLLal and its analogues. The curve fitting was performed using GraFit 4.0 for determination of IC50 values [15].

Table III.  IC₅₀ values for the inhibition of cathepsins B and L with ZLLLal and its analogues. The IC₅₀ values were obtained from Figures 2 and 3 using GraFit 4.0 for determination of IC₅₀ values [15].

	Inhibitor	IC50 (nM)
		Cathepsin B	Cathepsin L
a	ZLLLal	88	163
b	FuLLLal	21	44
c	NiLLLal	24	27
d	isoNiLLLal	12	20
e	MoSuLLLal	20	48
f	ZPLLal	84	116
g	ZPLLLal	319	205
h	AcPLLLal	39	57
i	ZPPLLLal	360	208
j	AcPPLLLal	40	19
k	ZLLLsc	690	407
l	ZPLLsc	154	79

Figure 3.  Inhibition of rat liver cathepsin L by ZLLLal and its analogues. The curve fitting was performed using GraFit 4.0 for determination of IC50 values [15].

RJ Leatherbarrow. GraFit Version 4.0. Staines, UK: Erithacus Software Ltd; (1998).

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