Alkaline phosphatase catalytic properties

We shall now briefly outline some of the features of the zinc metalloenzymes which have attracted most research effort several reviews are available, these are indicated under the particular enzyme, and for more detailed information the reader is referred to these. Attention is focussed here, albeit briefly, on carbonic anhydrases,1241,1262,1268 carboxypeptidases, leucine amino peptidase,1241,1262 alkaline phosphatases and the RNA and DNA polymerases.1241,1262,1462 Finally, we examine alcohol dehydrogenases in rather more detail to illustrate the use of the many elegant techniques now available. These enzymes have also attracted much effort from modellers of the enzymic reaction and such studies, which reveal much interesting coordination chemistry and often new catalytic properties in their own right—and often little about the enzyme system itself (except to indicate possibilities), will be mentioned in the next section of this chapter. 

The most important aspect of the study of Co(II) metalloenzymes is the possibility of using the metal ion as a functional, built-in reporter of the dynamics of the active site. The spectral and magnetic properties of Co (II) carbonic anhydrase have given valuable clues to the catalytic function of this enzyme. The recent studies of Co(II) alkaline phosphatase and Co (II) carboxypeptidase A indicate the general applicability of this approach to enzymes where the probe properties of the constitutive metal ion are poor. The comparison of the absorption spectra of these enzymes and low-molecular weight models have shown that the proteins provide irregular, and in some cases nearly tetrahedral environments. It is obvious, however, that a knowledge of the crystal structures of the enzymes is necessary before the full potential of this method can be exploited. 

B41. Brestkin, A. P., and Rzhekhina, N. I., On the effect of concentration and nature of the buffer solution upon the catalytic properties of alkaline phosphatase. Biokhimiya 30, 471-476 (1965). 

Isoenzymes are forms of an enzyme which are structurally different but have similar catalytic properties. Measurement of the isoenzymes of alkaline phosphatase and creatine kinase are of clinical value. 

The substitution of cobalt for the native zinc ions of alkaline phosphatase results in an active enzyme with distinctive optical properties, generated by the interaction of cobalt with the ligands of the protein. These properties may be employed to investigate the modes of binding of cobalt to the enzyme and also serve in a remarkable fashion to distinguish the catalytically essential metal atoms from those which play only a structural role. 

Cottam, G.L., A.D. Sherry, and K.M. Valentine, 1974a, Catalytic and spectroscopic properties of the lanthanide ion alkaline phosphatase complex, in Haschke, J.M. and H.A. Eick, eds.. Proceedings of the 11th Rare Earth Research Conference, Traverse City, Michigan, Vol. 1 (USAEC Technical Information Center, Oak Ridge, Tennessee) pp. 204-212. 

The alkaline phosphatase from calf intestinal mucosa (CIAP) has many catalytic properties in common with the BAP (see Section I,A, this chapter). CIAP is also a dimeric, Zn-metalloenzyme, but it has a slightly larger molecular size (130 kDa). One notable distinction is that CIAP is heat labile compared with BAP. This property alone makes the CIAP a valuable alternative to BAP in many applications requiring successive treatments with other enzymes. 

Phosphatase (Stepan and Ferwerda, 1973), acid phosphatase (Campbell et al, 1973), and alkaline phosphatase (Ramadose et al, 1974) were all found to exist in three forms, and in each case only one of the isoenzymes was susceptible to neuraminidase. In the case of alkaline phosphatase neuraminidase treatment of the sialic-acid-containing isoenzyme did not alter it with respect to reaction rate, affinity for substrates, or response to activators and inhibitors. The sialic acid residues thus seemed not to be essential to the catalytic properties of the isoenzyme, although it differed from the other two nonsialo species in thermal stability, metal ion effect, and affinity toward some substrates (Rama-... 

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