SPAI-1 

SPAI-1 is a specific inhibitor for monovalent cation transporting ATPases. SPAI-1 is a peptide isolated from porcine duodenum, inhibits Na⁺, K⁺-ATPase and H⁺, K⁺-ATPase in vitro, stimulates Mg²⁺-ATPase^[1][2].

SPAI-1 (10 nM; 2.5 hr) inhibits Na⁺, K⁺-ATPase by the competitive mode against Na⁺ and is uncompetitive with K⁺. The IC₅₀ of Na⁺, K⁺-ATPase inhibition effect is 0.12 μM^[1].
SPAI-1 (3-10 μM; 10 or 20 min) significantly inhibits Na⁺, K⁺-ATPase^[2].
SPAI-1 (0.1-100 μM; 10 or 20 min) shows light difference between enzyme preparations from dog and rat. As isoforms of Na⁺, K⁺-ATPase obtained from rats, SPAI-1 shows inhibition with IC₅₀s of 8.7-24.6 μM; as for isoforms of Na⁺, K⁺-ATPase obtained from dog, SPAI-1 shows inhibition with IC₅₀s of 11.6-17.5 μM^[2].
SPAI-1 (0.1-100 μM; 10 or 20 min) stimulates ouabain-insensitive Mg²⁺-ATPase at high concentration but failed to inhibit Ca²⁺-ATPase^[2].
SPAI-1 (0.01-50 μM; 10 or 20 min) also inhibits H⁺, K⁺-ATPase with an IC₅₀ value of 5 μM^[2].

MedChemExpress (MCE) has not independently confirmed the accuracy of these methods. They are for reference only.

5628.57

C₂₄₅H₃₈₆N₇₂O₆₅S₈

131359-77-8

LLSKRGHCPRILFRCPLSNPSNKCWRDYDCPGVKKCCEGFCGKDCLYPK (Disulfide bridge:Cys8-Cys37,Cys15-Cys41,Cys24-Cys36,Cys30-Cys45)

Room temperature in continental US; may vary elsewhere.

Please store the product under the recommended conditions in the Certificate of Analysis.

• [1]. Araki K, et al. Novel peptide inhibitor (SPAI) of Na+, K+-ATPase from porcine intestine. Biochem Biophys Res Commun. 1989 Oct 16;164(1):496-502.  [Content Brief]

  [2]. Ishizuka N, et al. Na+,K(+)-ATPase inhibition by an endogenous peptide, SPAI-1, isolated from porcine duodenum. Biochim Biophys Acta. 1991 Nov 4;1069(2):259-66.  [Content Brief]