Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.21.64 (proteinase K)
 4,071 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

C-terminal processing of low pI barley alpha-amylase (AMY1) results in multiple forms in malt, aleurone protoplasts, and transformed yeast. Expression of an AMY1 cDNA in yeast thus leads to four secreted forms with distinct pI values between 4.7 and 5.1 and essentially identical Mr. AMY1-1 and AMY1-2 lacking the C-terminal Arg-Ser are generated by carboxypeptidase in vitro from AMY1-3 and AMY1-4, respectively. In vivo processing is due to the KEX1-encoded yeast carboxypeptidase. AMY1-2 and AMY1-4 are fully active, whereas AMY+-1 and AMY1-3 retain 3-4% activity toward p-nitrophenyl maltoheptaoside and have one fewer SH group, due to reaction with glutathione. AMY1-1-AMY1-4 are indistinguishable from malt AMY1 with respect to Ca(2+)-, substrate-, and beta-cyclodextrin-binding as well as recognition by three monoclonal antibodies and limited proteolysis by proteinase K. Transient AMY1 precursors present in barley aleurone protoplasts were trapped by addition of serine carboxypeptidase inhibitors, indicating that endogenous carboxypeptidase participates in the maturation of AMY1 during germination. Three pairs of precursor/mature AMY1 forms are recognized, presumably corresponding to the three genes encoding AMY1. Malt carboxypeptidase II can convert in vitro the precursors isolated from protoplasts into processed enzyme, and AMY1 from malt accordingly lacks the C-terminal heptapeptide. This report thus demonstrates posttranslational protein modification by carboxypeptidase in higher plants.
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PMID:C-terminal processing of barley alpha-amylase 1 in malt, aleurone protoplasts, and yeast. 189 61

Leaves are reported to contain a secreted alpha-amylase that accumulates during senescence or after biotic or abiotic stress; however, a gene encoding this enzyme has not been described. Because a secreted amylase is isolated from plastidic starch, the function of this enzyme is difficult to predict, but circumstantial evidence suggests that it may degrade starch after cell death. The Arabidopsis thaliana genome contains three alpha-amylase genes, one of which, AMY1 (At4g25000), has a putative signal sequence suggesting that the protein may be secreted. Two independent T-DNA insertion mutants in AMY1 lacked an amylase band on starch zymograms, which was previously named 'A1'. Washed leaf protoplasts contained reduced A1 activity suggesting that the enzyme is secreted. Native AMY1, fused to a weakly fluorescent form of GFP, was sensitive to proteinase K infiltrated into leaf apoplastic spaces, while a cytosolic form of GFP was unaffected until cell breakage, confirming that the AMY1 protein is secreted. Amylase A1 was transcriptionally induced in senescing leaves and in leaves exposed to heat stress, treated with abscisic acid or infected with Pseudomonas syringae pv. tomato expressing avrRpm1. The A1 amylase was also extremely heat resistant and its expression was up-regulated in cpr5-2, an activated defence response mutant.
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PMID:An alpha-amylase (At4g25000) in Arabidopsis leaves is secreted and induced by biotic and abiotic stress. 1732 26