HA-100 (hydrochloride) (Synonyms: C-1)

HA-100 is a dechlorinated analogue of 1-(8-chloro-5-isoquinolinesulfonyl)piperazine (HA-156). HA-100 is an inhibitor of protein kinases (PKs) including PKA, PKC, and PKG [1].

Protein kinases are enzymes that can phosphorylate other proteins. Phosphorylation of proteins usually results in a functional change of the target protein (substrate) by changing enzyme activity, cellular location, or association with other proteins. Protein kinases operate in a large number of distinct signaling pathways, especially those involved in signal transduction. Protein kinases have also existed in bacteria and plant [2].

HA-100 inhibited the activity of PKA, PKC, and PKG with the IC50 values of 8, 12, and 4 μM, respectively. It showed less activity in blocking the activity of myosin light chain kinase with the IC50 of 240 μM [1]. HA-100 markedly decreased the affinity for MLC-kinase. HA-100 did not inhibit myosin light chain phosphorylation in platelets exposed to collagen significantly [1].

Reference:
[1] Hagiwara M, Inagaki M, Watanabe M, et al.  Selective modulation of calcium-dependent myosin phosphorylation by novel protein kinase inhibitors, isoquinolinesulfonamide derivatives[J]. Molecular pharmacology, 1987, 32(1): 7-12.
[2] Krebs E G.  Protein kinases[J]. Current topics in cellular regulation, 1972, 5: 99-133.