Macluralisin ? a serine proteinase from fruits of Maclura pomifera (Raf.) Schneid.

Abstract

A serine proteinase was isolated from fruits of Maclura pomifera (Raf.) Schneid. by affinity chromatography on bacitracin-containing sorbents and gel-filtration. The enzyme, named macluralisin, is a glycoprotein with a molecular mass of 65 kDa; its protein moiety corresponds to a molecular mass of 50 kDa. The substrate specificity of macluralisin towards synthetic peptides and insulin B-chain is similar to that of cucumisin, a subtilisin-like proteinase from melon fruit. The enzyme is completely inhibited by diisopropylfluorophosphate. Its amino-acid composition resembles that of a serine proteinase isolated from the Cucurbitaceae. The N-terminal sequence has 33% of its residues identical to those of the sequence of fungal subtilisin-like proteinase K. Hence, Maclura pomifera serine proteinase belongs to the subtilisin family, which seems to be broadly distributed in the plant kingdom.

LeSBT1, a Subtilase from Tomato Plants

“…In contrast to other plant subtilases (7,11,12,15), processing of proLeSBT1 did not result in zymogen activation. Maturation of LeSBT1 required the additional processing of 21 amino acids from its amino terminus.…”

“…Its NH 2 -terminal amino acid sequence beginning with a pair of threonine residues is highly similar to the amino termini that were determined for the mature, active cucumisin (7), P69 (15,31), lim9 (12), and macluralisin (11). Apparently, the processing site at the junction between the prodomain and the catalytic domain is well conserved in plant subtilases (18).…”

“…While LeSBT1 exhibited preference for Gln in the P 1 position of its substrate, this residue was not absolutely required. Cleavage of glucagon-(1-24) to yield glucagon- (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15) indicates that Asp is tolerated in the P 1 position. However, cleavage carboxylterminal of Asp and accumulation of glucagon-(1-15) was slow except at pH 4.5 to 4.0 (Fig.…”

“…Unlike the kexins, cucumisin does not exhibit a preference for substrates with paired basic residues. Its substrate specificity was shown to be broad and similar to that of bacterial subtilisins (8,9) and the plant proteases taraxalisin (10) and macluralisin (11). In recent years, genomic and cDNA sequences have been obtained for many plant subtilases from members of genera as diverse as Lilium (12) Alnus (13), Arabidopsis (13,14), and Lycopersicon (15)(16)(17)(18).…”

Fibrin(ogen)olytic and antiplatelet activities of a subtilisin-like protease from Solanum tuberosum (StSBTc-3)

“…A comparable cleavage pattern was observed in the course of insulin b-chain hydrolysis with plant serine proteases from Cucumis melo, Trichosanthes cucumeroides, Parthenium agentatum, Maclura pomifera (named as Macluralisin). As reported for a serine protease isolated from Helianthus annuus, a fungal proteinase A1 from Trichosanthes cucumeroides and human plasmin [40,41], StSBTc-3 hydrolyzes the amino acid bond between Arg22-Gly23 (Fig. 4).…”