Involved in plant defense (PubMed:18328522). Inhibits spore germination in C.sojina, A.niger (at concentrations >50 ug/ml) and P.herguei but not in F.oxysporum and F.solani (PubMed:20831249, PubMed:18328522). Does not inhibit vegetative mycelial growth (PubMed:20831249). Inhibits growth of C.albicans and K.marxiannus but not P.membranifaciens or C.parapsilosis (PubMed:20831249, PubMed:23894655). Probably acts by affecting the cell membrane (PubMed:20831249). Does not have urease, chitinase, beta-1,3-glucanase or hemagglutination activities (PubMed:18328522, PubMed:20831249). Does not inhibit trypsin (PubMed:18328522). Injection into mice produces toxic effects such as dyspnea, tonic-clonic convulsion and death (PubMed:18328522). Activity decreases below pH 5.5 and above pH 8.0. Heterodimer of a 27 kDa subunit and a 17 kDa subunit; disulfide-linked. Expressed in seeds, leaves, roots and stem (at protein level). In seeds, induced by jasmonate. SBTX is known to be glycosylated but it is not known which one of its two subunits is modified; contains 5% carbohydrates. LD(50) is 5.6 mg/kg by intraperitoneal injection into mice. On the 2D-gel the determined pI of SBTX is: 8.2, its MW is: 44 kDa.