Neutrophil Elastase Activity Imaging: Recent Approaches in the Design and Applications of Activity-Based Probes and Substrate-Based Probes

Table 1

Recapitulative set of probes for NE proteolytic activity imaging.

Probe sequence	kcat/KM(M^−1·s^−1)	KM(μM)	kcat(s^−1)	Nature of probe	Detection modality	Probe name	References
^99mTC-NX21909	2 × 10^5 (kinact)			Activity-based probe	Positron emission tomography	NX21909	[33]
^99mTC-MAG3-EPI-HNE-2	2 × 10^−6 (Ki)			Activity-based probe	Positron emission tomography	EPI-HNE-2	[34]
Biotin-PEG(4)-Nle(O-bzl)-Met(O2)-Oic-AbuPO(Oph)2	1.4 × 10^7 (kobs/I)	n.d	n.d	Activity-based probe	Optic (fluorogenic)	Elastase-PK101	[35, 36]
Ac-AAPV-AMC	5.8 × 10^3	n.d	n.d	Substrate-based probe	Optic (fluorogenic)	—	[37]
MeO-Suc-AAPV-AMC	11 × 10^3	290	3.3	Substrate-based probe	Optic (fluorogenic)	—	[37]
CFP-TSGGSGGTRQFIRWGGGGSGGTTG-YFP-HHHHHH	390 × 10^5 (kobs/KM)	0.7 ± 0.2	27 ± 5.4 (kobs)	Substrate-based probe	Optic (fluorogenic)	Protein Biosensor IV	[38]
Abz-QPMAVVQSVPQ-EDDnp	10.9 × 10^5	n.d	n.d	Substrate-based probe	Optic (fluorogenic)	NEmo-1 & NEmo-2	[39, 40]
						Neutrophil Elastase 680 FAST^™	[41–45]
CNC-(O-C(O)G-NHC(O)-Suc-APA-AMC	33.5 × 10^5	n.d	n.d	Substrate-based probe	Optic (fluorogenic)	PepNA	[46]
MeO-Suc-AAPV-(R/S)C12H23NO5P^▪				Substrate-based probe	MRI (dynamic nuclear polarization)	—	[47]
R-isomer	9.3 × 10^5	15 ± 2.9	14 ± 0.9
S-isomer	6.4 × 10^5	25 ± 5.4	16 ± 1.1

n.d., no data.