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The soluble protein fraction prepared from mandelate grown cells of Pseudomonas fluorescens as described in a previous paper (Gunsalus et al., 1953) contains four enzymes which are involved in the conversion of DL-mandelic acid to benzoic acid. These are: mandelic acid racemase, benzoylformic carboxylase, and two benzaldehyde dehydrogenases, linked respectively to diphosphopyridine nucleotide (DPN) and triphosphopyridine nucleotide (TPN). This paper describes the separation of these four enzyme activities and some of their properties. METHODS Assays. Benzoylformic carboxylase was assayed manometrically by measuring the rate of carbon dioxide evolution from benzoylformic acid at pH 6.0 and 30 C. The test system contained 100 ug of cocarboxylase, 50 iM of sodium benzoyl

rnethremoglobin and oxyhremoglobin can be demonstrated simply by shaking these solutions with chloroform, when only the former is denatured and is precipitated. When the water molecule bound to iron in methremoglobin is replaced by fluoride or azide ions, however, tho pigment acquires resistance to chloroform treatment. These results are exactly parallel to those observed in the desiccation experiments, which demornitrated an increased resistance of hmmoglobin and methromoglobin to denaturation when their iron-bound water molecules are replaced by oxygen, f-Ju01•ido or azi(le.Tho reactions taking place during the cfrying of Ju:emoglobin and methoomoglobin, although perfectly reversible, appear to be of a more complex nature than the simple polymerimtion envisaged by Haurowitz 2 , and to involve reversible changes in tht, architecture of the whole hrornoprotein molecul0.