Arginine deiminase from Mycoplasma arthritidis. Evidence for multiple forms

Area of Science:

• Biochemistry
• Enzymology
• Microbiology

Background:

• Arginine deiminase (EC 3.5.3.6) is an enzyme crucial in microbial metabolism.
• Mycoplasma arthritidis ATCC 14152 is a known producer of arginine deiminase.

Purpose of the Study:

• To purify and characterize arginine deiminase from Mycoplasma arthritidis ATCC 14152.
• To investigate the different forms of arginine deiminase produced by this bacterium.
• To explore the interconversion and properties of these enzyme forms.

Main Methods:

• Enzyme purification using protamine sulfate fractionation and DEAE-agarose chromatography.
• Homogeneity assessment via gel filtration, SDS-PAGE, NH2-terminal analysis, and PAGE.
• Characterization of enzyme properties including molecular weight, isoelectric point, and substrate affinity (Km).

Main Results:

• A 6-fold purification of arginine deiminase was achieved with high yield (75-85%).
• Two distinct native forms (deiminase I and II) were identified, differing in isolation phase, chromatographic behavior, electrophoretic mobility, specific activity, and spectral ratios.
• A third form (deiminase III) was generated from deiminase II, exhibiting increased specific activity and properties similar to deiminase I, without changes in molecular weight or subunit structure.

Conclusions:

• Mycoplasma arthritidis produces multiple, distinct forms of arginine deiminase.
• Deiminase II can be converted to deiminase III, suggesting a post-translational modification or conformational change that enhances activity.
• The characterization provides insights into the enzyme's structure-function relationship and potential regulatory mechanisms.