Open AccessPhoN‐type acid phosphatases of a heavy metal‐accumulating Citrobacter sp.: resistance to heavy metals and affinity towards phosphomonoester substrates
Author(s) -
Jeong B.C.,
Macaskie L.E.
Publication year - 1995
Publication title -
fems microbiology letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.899
H-Index - 151
eISSN - 1574-6968
pISSN - 0378-1097
DOI - 10.1111/j.1574-6968.1995.tb07722.x
Subject(s) - metal , chemistry , phosphatase , heavy metals , biochemistry , nuclear chemistry , environmental chemistry , phosphorylation , organic chemistry
An atypical Citrobacter sp. isolated from a heavy metal‐polluted site has a PhoN‐type acid phosphatase that is responsible for the precipitation of heavy metals as cell‐bound metal phosphates via liberated inorganic phosphate, supplied via enzymic cleavage of a phosphomonoester substrate. Phosphatase activity, comprising two isoenzymes designated CPI and CPII, was resistant to cadmium (II), zinc (II) and lead (II), but sensitive to uranyl and vanadyl oxycations and cupric ion. The monovalent cations of mercury (I) and silver (I), and trivalent yttrium (III) were inhibitory, particularly to CPII. Theanionic counterion did not influence metal toxicity. The K m of CPII towards some phosphomonoester substrates was higher than than that of CPI, suggesting that although the two isoenzymes were shown previously to be closely related, subtle differences exist between them that justify their classification as separate isoenzymes, for which the physiological function is still obscure.