0000000000185941
AUTHOR
Leena Mikola
Occurrence of acid and neutral carboxypeptidases in germinating cereals
High neutral metallocarboxypeptidase activity (EC 3.4.17) has earlier been detected in young seedlings of rice (Oryza sativa L.) using benzyloxycarbonyl-L-phenylalanyl-L-alanine (Z-Phe-Ala) as substrate at pH 7. This finding was confirmed, and it was observed that the activity could be assayed with higher specificity and sensitivity by using Z-Gly-Ala or Z-Gly-Phe as substrate at pH 6.5–7. No corresponding activity was detected in seedlings of barley (Hordeum vulgare L. cv. Himalaya), oats (Avena sativa L.) or maize (Zea mays L.). The seedlings of the four cereals possessed similar activities of acid carboxypeptidases (EC 3.4.16; hydrolysis of Z-Phe-Ala and Z-Ala-Phe at pH 5.2 and of Z-Ala-…
Mobilization of proline in the starchy endosperm of germinating barley grain.
In germinating grains of barley, Hordeum vulgare L. cv. Himalaya, free proline accumulated in the starchy endosperm during the period of rapid mobilization of reserve proteins. When starchy endosperms were separated from germinating grains and homogenized in a dilute buffer of pH 5 (the pH of the starchy endosperm), the liberation of proline continued in these suspensions. The process was completely inhibited by diisopropylfluorophosphate, indicating that it was totally dependent on serine carboxy-peptidases. The carboxypeptidases present in the starchy endosperms of germinating grains were fractionated by chromatography on DEAE-cellulose. Four peaks were obtained, all with different activi…
Acid Carboxypeptidases in Grains and Leaves of Wheat, Triticum aestivum L
Extracts of resting and germinating (3 days at 20 degrees C) wheat (Triticum aestivum L. cv Ruso) grains rapidly hydrolyzed various benzyloxycarbonyldipeptides (Z-dipeptides) at pH 4 to 6. Similar activities were present in extracts of mature flag leaves. Fractionation by chromatography on CM-cellulose and on Sephadex G-200 showed that the activities in germinating grains were due to five acid carboxypeptidases with different and complementary substrate specificities. The wheat enzymes appeared to correspond to the five acid carboxypeptidases present in germinating barley (L Mikola 1983 Biochim Biophys Acta 747: 241-252). The enzymes were designated wheat carboxypeptidases I to V and their …
Aspartic Proteinase from Barley Seeds is Related to Animal Cathepsin D
In contrast to the well-characterized mammalian aspartic proteinases, plant aspartic proteinases have received little attention so far. Aspartic proteinase activity has been detected, for example, in resting seeds of scots pine (Salmia et al., 1978), soybean (Bond & Bowles, 1983), barley and wheat (Morris et al., 1985) as well as in leaves of orange (Garcia-Martinez & Moreno, 1986) and barley (Kervinen et al., 1990). Aspartic proteinases have been purified from the seeds of rice (Doi et al., 1980), cucumber, squash (Polanowski et al 1985) and wheat (Dunaevsky et al., 1989) as well as from the leaves of tomato (Rodrigo et al., 1989). The plant aspartic proteinases have been reported to enhan…
Aspartic proteinase from barley grains is related to mammalian lysosomal cathepsin D
Resting barley (Hordeum vulgare L.) grains contain acid-proteinase activity. The corresponding enzyme was purified from grain extracts by affinity chromatography on a pepstatin-Sepharose column. The pH optimum of the affinity-purified enzyme was between 3.5 and 3.9 as measured by hemoglobin hydrolysis and the enzymatic activity was completely inhibited by pepstatin a specific inhibitor of aspartic proteinases (EC 3.4.23). Further purification on a Mono S column followed by activity measurements and sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed that the affinity-purified enzyme preparation contained two active heterodimeric aspartic proteinases: a larger 48k Da enzyme, c…