SummaryAlthough the interconversion between C4 and C3 compounds has an important role in overall metabolism, limited information is available on the properties and regulation of enzymes acting on these metabolites in hyperthermophilic archaea. Malic enzyme is one of the enzymes involved in this interconversion, catalyzing the oxidative decarboxylation of malate to pyruvate as well as the reductive carboxylation coupled with NAD(P)H. This study focused on the enzymatic properties and expression profile of an uncharacterized homolog of malic enzyme identified in the genome of a heterotrophic, hyperthermophilic archaeon Thermococcus kodakaraensis KOD1 (Tk-Mae). The amino acid sequence of Tk-Mae was 52-58% identical to those of malic enzymes from bacteria, whereas the similarities to the eukaryotic homologs were lower. Several catalytically important regions and residues were conserved in the primary structure of Tk-Mae. The recombinant protein, which formed a homodimer, exhibited thermostable malic enzyme activity with strict divalent cation dependency. The enzyme preferred NADP + rather than NAD + , but did not catalyze the decarboxylation of oxaloacetate, unlike the usual NADP-dependent malic enzymes. The apparent Michaelis constant (K m ) of Tk-Mae for malate (16.9 mM) was much larger than those of known enzymes, leading to no strong preference for the reaction direction. Transcription of the gene encoding Tk-Mae and intracellular malic enzyme activity in T. kodakaraensis were constitutively weak, regardless of the growth substrates. Possible roles of Tk-Mae are discussed based on these results and the metabolic pathways of T. kodakaraensis deduced from the genome sequence.
Abstract. Rahayu S, Fitri L, Ismail YS. 2019. Short communication: Endophytic actinobacteria isolated from ginger (Zingiber officinale) and its potential as a pancreatic lipase inhibitor and its toxicity. Biodiversitas 20: 1312-1317. Endophytic actinobacteria from ginger (Zingiber officinale Rosc.) is a bacterium that is capable of producing secondary metabolites that are the same as their hosts. This study aims to look at the potential of endophytic actinobacteria from ginger as a pancreatic lipase inhibitor and its toxicity. Endophytic actinobacteria were isolated, purified, then tested for pancreatic lipase inhibitors and their toxicity using the BSLT method (Brine Shrimp Lethality Test) and phytochemical tested on ethanol extract of selected isolates. Seven endophytic actinobacterial isolates were isolated from the ginger rhizome. The isolates had different morphological diversity based on colony and microscopic observations and 5 isolates had pancreatic lipase inhibitor activity. The highest inhibitors were found in AJ4 isolates (89.9%), compared with pancreatic lipase inhibitors crude extracts of ginger (68.9%) and orlistat (88.1%) as positive controls. The LC50 value of AJ4 isolates was 653,381 ppm and the value of LT50 was 17,569 hours. AJ4 isolates contain terpenoids, phenols, tannins, flavonoids, alkaloids, and saponins. This research data is considered as new information about the potential of endophytic actinobacteria from ginger as pancreatic lipase inhibitors and their toxicity.
Abstract. Fitri L, Putri KA, Suhartono, Ismail YS. 2019. Short Communication: Isolation and characterization of thermophilic actinobacteria as proteolytic enzyme producer from Ie Seuum Hot Spring, Aceh Besar, Indonesia. Biodiversitas 20: 2802-2808. Proteases are enzymes who catalyze the breakdown of peptide bonds in proteins. This enzyme could be produced from thermophilic bacteria that are able to grow at temperatures of 45-80ºC and are stable to heat. The samples were collected at Ie Seu'um hot spring, Aceh Besar. This study aimed to isolate, to characterize and to determine actinobacteria that were capable of producing protease enzymes. The sampling method in this study was conducted by purposive sampling at temperatures of 50, 60 and 70ºC. Isolation of thermophilic actinobacteria was carried out in Humic Acid Vitamin B (HV) Agar medium and morphological characterization was carried out in Yeast Malt Agar (YMA), Yeast Starch Agar (YSA), Oatmeal Agar (OA) media. Microscopic characterization and measurement of clear zone diameter formed were carried out in skim milk medium. The results showed that one actinobacteria isolate was obtained at a temperature of 50ºC and five isolates at a temperature of 60ºC, meanwhile, no actinobacteria could be obtained at a temperature of 70ºC. A total of 4 isolates obtained were able to produce protease enzymes. The highest Proteolytic Index (IP) value was obtained from IS01 which was 3.8.
<p>Plant growth promoting rhizobacteria (PGPR) are a group of beneficial bacteria that live in rhizosphere. These bacteria can promote plant growth through several mechanisms, such as the ones produce indole-3-acetic acid (IAA) hormone and hydrogen cyanide (HCN), and act as biocontrol agents. The use of PGPR to promote plant growth has been known to be an environmentally friendly alternative approach. The aim of this study was to explore IAA and HCN producing rhizobacteria from cassava rhizosphere soil and identify the bacteria based on morphological and biochemical characters, hypersensitive reaction test, and the ability test to produce IAA and HCN. The results showed nine bacterial isolates suspected as Micrococcus sp. (six isolates), Neisseria sp. (two isolates), and Bacillus sp. (one isolate). All isolates were able to produce IAA in the concentration range of 50,63–135,00 µg/ml and 232,3–333,9 µg/ml at incubation time of 2 and 4 days, respectively. All isolates were able to produce HCN. In addition, the isolates did not show hypersensitivity reactions. Further study is needed to assess the isolate application for promoting plant growth as well as a biocontrol agent of plant pathogen.</p>
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