Structure and Stability of the Potato Cysteine Protease Inhibitor Group (Cv. Elkana)

Abstract

The conformational stability of potato cysteine protease inhibitor (PCPI), the second most abundant protease inhibitor group in potato tuber, was investigated at ambient temperature and upon heating using far- and near-UV circular dichroism spectroscopy, fluorescence spectroscopy, and differential scanning calorimetry (DSC). The PCPI isoforms investigated have a highly similar structure at both the secondary and the tertiary level. PCPI isoforms show structural properties similar to those of the potato serine protease inhibitor group and the Kunitz type soybean trypsin inhibitor, a known beta-II protein. Therefore, PCPI isoforms are also classified as members of the beta-II protein subclass. Results show that the thermal unfolding of PCPI isoforms does not follow a two-state mechanism and that at least one intermediate is present. The occurrence of this intermediate is most apparent in the thermal unfolding of PCPI 8.3 as indicated by the presence of two peaks in the DSC thermogram. Additionally, the formation of aggregates (>100 kDa), especially at low scan rates, increases the apparent cooperativity of the unfolding.

Comparison of composition, enzyme activity and selected functional properties of potato proteins isolated from potato juice with two different expanded bed resins

“…It has been shown that a-helical parts of patatin unfold in the 45-55 C region, whereas the b-stranded parts unfold more gradually from 50 to 90 C (Pots, de Jongh, Gruppen, Hamer, & Voragen, 1998). The heat-induced conformational changes of the two main protease inhibitor groups, PSPI and PCPI, have also been investigated previously Pouvreau, Kroef, et al, 2005). The authors reported T-max around 62-67 C for the two protease inhibitor groups, which corresponds well with the Tmax of concentrate B.…”

“…Protease inhibitors (5-25 kDa) with pI's between 5.1 and 9.0 (Pouvreau et al, 2001) and other proteins of higher molecular weights make up the other major proteins (Pots et al, 1999). The two major groups of protease inhibitors are the potato serine protease inhibitors (PSPI) and the potato cystein protease inhibitors (PCPI) with molecular masses of 20.5 and 21.0, respectively Pouvreau, Kroef, et al, 2005). Potato proteins are well balanced in their amino acid composition, comparable to milk and egg protein (Knorr, 1982).…”

Teaching Enzyme Activity to the Visual Impaired and Blind Students

“…Pineapple juice bromelain is active in acidic pH, with an optimum pH range of between 4 and 6 ( Figure 3C). For the bromelain inhibition ( Figure 3D), we used the juice of potato tubers that is rich in potato cysteine proteinase inhibitor, PCPI [27].…”

Patates Protei̇nleri̇

“…Proteaz inhibitörleri, besin sindirimini engelleme özelliklerinin yanı sıra anti-kanserojen etki ve kolesitokinin oluşturma potansiyeline de sahiptirler. Sahip oldukları di-sülfit bağlarının koruyucu etkileri sayesinde pH 3,0-7,5 aralığında üç boyutlu yapılarında herhangi bir değişim gözlenmez [24].…”