Some Properties of Acid Protease from the Thermophilic Fungus, Penicillium duponti K1014

Abstract

A purified acid protease from a true thermophilic fungus, Penicillium duponti K1014, was most active at pH 2.5 for milk casein and at pH 3.0 for hemoglobin. The enzyme was stable at a pH range of 2.5 to 6.0 at 30 C for 20 h. The acid protease retained full activity after 1 h at 60 C at a pH range between 3.5 and 5.5. At the most stable pH of 4.5, more than 65% of its activity remained after heat treatment for 1 h at 70 C. These thermal properties show the enzyme as a thermophilic protein. The enzyme activity was strongly inhibited by sodium lauryl sulfate and oxidizing reagents such as potassium permanganate and N-bromosuccinimide. No inhibition was caused by chelating reagents, potato inhibitor, and those reagents which convert sulfhydryl groups to mercaptides. Reducing reagents showed an activating effect. The enzyme showed the trypsinogen-activating property at an acidic pH range; optimal trypsinogen activation was obtained at a pH of approximately 3.0. The isoelectric point of the enzyme was estimated to be pH 3.89 by disk electrofocusing. By using gel filtration, an approximate value of 41,000 was estimated for the molecular weight.

Biochemical and Functional Characterization of a Metalloprotease from the Thermophilic FungusThermoascus aurantiacus

“…Other researches , show that optimum temperatures for fungal proteases vary from 40 to 60 °C. However, proteases from thermophilic fungi show higher values for optimum temperature such as 70 and 75 °C, as shown in the studies of Li et al with Thermomyces lanuginosus and Hashimoto et al with Penicillium duponti K1014, respectively, which agrees with our results.…”

“…There are reports of protease purification through the use of traditional procedures that involve precipitation and chromatographic techniques, and the low molecular mass exhibited by the protease is in agreement with other research in which fungal proteases are generally lower than 50 kDa ,, . Differently from other authors, the purification protocol we achieved did not employ ion exchange chromatography.…”

“…Thermophilic fungi are characterized by exhibiting minimal growing temperature of 20 °C and maximum growing temperature of 55 °C and generally produce enzymes with some important characteristics such as higher thermostability, optimum activity at elevated temperatures and high hydrolysis rates , . Many researchers have described thermostable protease production by bacteria , ; however, the reports of thermostable protease production by thermophilic fungi are few and old − .…”

Optimization of Acid Protease Production byAspergillus nigerI1 on Shrimp Peptone Using Statistical Experimental Design

“…spinosa IBT 4872 [ 45 ]. Proteases from R. oryzae [ 43 ], P. duponti K1014 [ 46 ], P. oxalicum [ 47 ], and Cryptococcus albidus [ 48 ] exhibited optimum activity at 60°C.…”

Aspartic protease from Aspergillus (Eurotium) repens strain MK82 is involved in the hydrolysis and decolourisation of dried bonito (Katsuobushi)

“…The synthesis of this factor, aspartic protease, by A. repens strain MK82 was promoted when the culture was grown with high concentrations of d ‐glucose. Protease production would probably also be affected by osmotic pressure or water activity, since several fungi are strongly influenced by the moisture content of the growth substrate in solid state cultures . For example, Aspergillus flavus IMI 327634 synthesised more extracellular protease in semisolid culture (substrate moisture 630 g kg −1 ) than in liquid culture, and an Aspergillus strain produced more cellulose‐ and xylan‐degrading enzymes at low moisture content (330 g kg −1 )…”