tailieunhanh - Báo cáo khoa học: Two beta-alanyl-CoA:ammonia lyases in Clostridium propionicum

The fermentation ofb-alanine by Clostridium propionicumproceeds via activation to the CoA-thiol ester, followed by deamination to acryloyl-CoA, which is also an intermediate in the fermentation ofl-alanine. By shifting the organism from the carbon and energy source a-alanine to b-alanine, the enzyme b-alanyl-CoA:ammonia lyase is induced 300-fold ( 30% of the soluble protein). The low basal lyase activity is encoded by theacl1gene, whereas the almost identicalacl2gene (six amino acid substi-tutions) is responsible for the high activity after growth on b-alanine | ềFEBS Journal Two beta-alanyl-CoA ammonia lyases in Clostridium propionicum Gloria Herrmann1 Thorsten Selmer1 Holly J. Jessen2 Ravi R. Gokarn2 Olga Selifonova2 Steve J. Gort2 and Wolfgang Buckel1 1 Laboratorium fur Mikrobiologie Fachbereich Biologie Philipps-Universitat Marburg Germany 2 Biotechnology Development Center CargillIncorporated Minneapolis MN USA Keywords acryloyl-CoA beta-alanyl-CoA CoA-transferase L-alanine and beta-alanine fermentation pentamer Correspondence W. Buckel Laboratorium fur Mikrobiologie Fachbereich Biologie Philipps-Universitat 35032 Marburg Germany Fax 49 64212828979 Tel 49 6421 28 21527 E-mail buckel@ Received 15 October 2004 revised 24 November 2004 accepted 7 December 2004 doi The fermentation of b-alanine by Clostridium propionicum proceeds via activation to the CoA-thiol ester followed by deamination to acryloyl-CoA which is also an intermediate in the fermentation of L-alanine. By shifting the organism from the carbon and energy source a-alanine to b-alanine the enzyme b-alanyl-CoA ammonia lyase is induced 300-fold w 30 of the soluble protein . The low basal lyase activity is encoded by the acll gene whereas the almost identical acl2 gene six amino acid substitutions is responsible for the high activity after growth on b-alanine. The deduced b-alanyl-CoA ammonia lyase proteins are related to putative b-aminobutyryl-CoA ammonia lyases involved in lysine fermentation and found in the genomes of several anaerobic bacteria. b-Alanyl-CoA ammo-nia lyase 2 was purified to homogeneity and characterized as a heteropentamer composed of 16 kDa subunits. The apparent Km value for acryloyl-CoA was measured as 23 4 pM independent of the concentration of the second substrate ammonia kcat Km was calculated as 107 M-1-s-1. The apparent Km for ammonia was much higher 70 5 mM at 150 IM acry-loyl-CoA with a much lower kcat Km of 4 X 103 M-1-s-1. In the reverse reaction a Km of 210 30 pM was .