Human angiotensin-converting enzyme-related carboxypeptidase (ACE2) is a zinc metalloprotease whose closest homolog is angiotensin I-converting enzyme. To begin to elucidate the physiological role of ACE2, ACE2 was purified, and its catalytic activity was characterized. ACE2 proteolytic activity has a pH optimum of 6.5 and is enhanced by monovalent anions, which is consistent with the activity of ACE. ACE2 activity is increased ϳ10-fold by Cl ؊ and F ؊ but is unaffected by Br ؊ . ACE2 was screened for hydrolytic activity against a panel of 126 biological peptides, using liquid chromatographymass spectrometry detection. Eleven of the peptides were hydrolyzed by ACE2, and in each case, the proteolytic activity resulted in removal of the C-terminal residue only.

The angiotensin-converting enzyme (ACE)-related carboxypeptidase, ACE2, is a type I integral membrane protein of 805 amino acids that contains one HEXXH ؉ E zincbinding consensus sequence. ACE2 has been implicated in the regulation of heart function and also as a functional receptor for the coronavirus that causes the severe acute respiratory syndrome (SARS). To gain further insights into this enzyme, the first crystal structures of the native and inhibitor-bound forms of the ACE2 extracellular domains were solved to 2.2-and 3.0-Å resolution, respectively. Comparison of these structures revealed a large inhibitor-dependent hinge-bending movement of one catalytic subdomain relative to the other (ϳ16°) that brings important residues into position for catalysis. The potent inhibitor MLN-4760 ((S,S)-2-{1-carboxy-2-[3-(3,5-dichlorobenzyl)-3H-imidazol4-yl]-ethylamino}-4-methylpentanoic acid) makes key binding interactions within the active site and offers insights regarding the action of residues involved in catalysis and substrate specificity. A few active site residue substitutions in ACE2 relative to ACE appear to eliminate the S 2 substrate-binding subsite and account for the observed reactivity change from the peptidyl dipeptidase activity of ACE to the carboxypeptidase activity of ACE2.The angiotensin-converting enzyme (ACE) 1 -related carboxypeptidase, ACE2, is a type I integral membrane protein of 805 amino acids that contains one HEXXH ϩ E zinc-binding consensus sequence (1, 2). The catalytic domain of ACE2 is 42% identical to that of its closest homolog, somatic angiotensinconverting enzyme (sACE; EC 3.4.15.1), a peptidyl dipeptidase that plays an important role in the renin angiotensin system for blood pressure homeostasis. The loss of ACE2 in knockout mice has no effect on blood pressure, but reveals ACE2 as an essential regulator of heart function (3). In a recent discovery, ACE2 was identified as a functional receptor for the coronavirus that is linked to the severe acute respiratory syndrome (SARS) (4, 5).The physiological differences observed in the phenotypes of ACE (6, 7) and/or ACE2 (3) knockout mice presumably reflect the significant differences in substrate specificity and reactivity between these enzymes. Many substrates for ACE2 were identified by screening biologically active peptides (8). In all cases, only carboxypeptidase activity was found. Of the seven best in vitro peptide substrates identified (k cat /K m Ͼ 10 5 M Ϫ1 s Ϫ1 ), proline and leucine are the preferred P 1 residues, with a partiality for hydrophobic residues in the P 1 Ј position, although basic residues at P 1 Ј are also cleaved (peptide-binding subsites in proteins are as previously defined (9)). Some of the best in vitro peptide substrates are apelin-13, des-Arg 9 -bradykinin, angiotensin II, and dynorphin A-(1-13). The longest peptide substrate identified is a 36-residue peptide, apelin-36 (8). An examination of the ACE2 and ACE literature may be found in recently published reviews (10 -12).We report here the first crystal ...

The data provided a comprehensive survey of insecticide resistance in Bactrocera dorsalis in mainland China. All results suggested that early resistance management programmes should be established for restoring the efficacy of pesticide-based control measures.

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The objectives of this study were to clarify the effect of chemical fertilizer and manure application on methane (CH 4 ) and nitrous oxide (N 2 O) emissions from intensively managed grassland on Andosols in Japan and to determine the controlling factors of the CH 4 and N 2 O emissions. The emission factors (EF) for both fertilizerand manure-induced N 2 O emissions were calculated. Three experimental plots were set up in five grasslands across four climatic regions in Japan: one plot for treatment with chemical fertilizer (fertilizer plot); another plot for treatment with cattle manure and chemical fertilizer (manure plot), and the final plot was not treated with chemical fertilizer or manure (control plot). The type of chemical fertilizer was ammonium-based fertilizer or a combination fertilizer of ammonium and urea. CH 4 and N 2 O emissions were measured at the study sites for six years. For the manure plot, a supplement of chemical fertilizer was added to equalize the supply rate of mineral nitrogen (N) relative to that of the fertilizer plots. There were no significant differences in CH 4 emissions among the treatment plots, and the effect of fertilizer or manure application was not evident. CH 4 emissions tended to be larger at sites with higher soil moisture content. The application of chemical fertilizer or manure increased N 2 O emissions at all the sites, and there were significant differences among the sites and across different years. Background N 2 O emissions (N 2 O emissions at the control plot) had strong positive correlations with air temperature and precipitation, along with weak positive correlations with soil carbon and N content. Therefore, an empirical model (Background N 2 O emission ¼ 0.298 Â air temperature þ 0.512 Â soil N content À3.77) was established. Fertilizer-induced N 2 O emission factor (EF) had a positive correlation (R 2 ¼ 0.50, p < 0.01) with precipitation (Fertilizer-induced EF ¼ 0.0022 Â precipitation À1.3), and increasing precipitation enhanced N 2 O production through the denitrification process due to applied fertilizer N. There were no significant differences in manure-induced EFs among the sites, and the average was 0.36% except for an outlier.

-N with and without the addition of glucose had a significantly positive correlation with soil pH (P < 0.05). Soil pH was significantly influenced by N source, which was significantly lower in the chemical fertilizer plot than in the control and manure plots. For a fixed quantity of available N, the application of manure could result in higher N 2 O emission compared with chemical fertilizer, owing to higher soil pH values under manure application than under chemical fertilizer application.

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