Nonhydrolytic proteins

Since essentially all of the protein in the cellulose-grown culture or the sophorose-incubation mixture can be accounted for by the three principal proteins and the / -glucosidase, it seems reasonable to conclude that the multiplicity of enzymes seen after several days of culture growth are caused by degradation. This may be attributable either to inherent instability (3) or to the presence of hydrolytic enzymes (16). There seems to be no evidence for the Ci enzyme as a nonhydrolytic or affinity factor, since all known enzymes of the system are hydrolytic. That the sophorose-stimulated system (with no possible loss of the Ci ... 

For the purpose of this chapter, enzyme-catalyzed modifications of proteins will be divided into two groups hydrolytic and nonhydrolytic reactions. Generally speaking, post-translational reactions occurring in vivo are catalyzed by highly specific enzymes under rather restricted conditions in contrast with in vitro modifications which are carried out under less specific conditions. 

These nonhydrolytic, post-translational enzymatic modifications of proteins, described in two recent publications (9,10), will not be treated further in this chapter. Hydrolytic modification, in vivo and in vitro, is the single most frequently occurring enzymatic modification of proteins. 

Table II. Enzyme-Catalyzed Nonhydrolytic Modifications of Proteins...

A third enzyme, ADP-ribosyl protein lyase, catalyzes the nonhydrolytic cleavage of protein proximal ADPR residues yielding the unique nucleotide ADP-3"-deoxy-pentos-2"-ulose (ADP-DP). In addition to the basic enzymology shown in Figure 1, related enzyme activities... 

More structural data for cellulose-type linkage geometries are available from crystals of proteins that are complexed with either cellulose fragments or molecules that contain a lactose moiety. Figure 15-10 shows a complex of cellotetraose and an endoglucanase (Sakon et al. 1996), as well as the structure of the fragment in more detail. That protein is an enzyme that catalyzes the hydrolysis of cellulose molecules, but it also has nonhydrolytic binding sites. Other proteins do... 

Banka, RR Mishra, S Chose, TK. Fibril formation from cellulose by a novel protein from Trichoderma reesei A nonhydrolytic cellulolytic component World J Microbiol Biotechnol, 1998, 14, 551-8. 

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