  We review enzymatic systems which involve biocatalytic reactions utilized for
information processing (biocomputing). Extensive ongoing research in
biocomputing, mimicking Boolean logic gates has been motivated by potential
applications in biotechnology and medicine. Furthermore, novel sensor concepts
have been contemplated with multiple inputs processed biochemically before the
final output is coupled to transducing "smart-material" electrodes and other
systems. These applications have warranted recent emphasis on networking of
biocomputing gates. First few-gate networks have been experimentally realized,
including coupling, for instance, to signal-responsive electrodes for signal
readout. In order to achieve scalable, stable network design and functioning,
considerations of noise propagation and control have been initiated as a new
research direction. Optimization of single enzyme-based gates for avoiding
analog noise amplification has been explored, as were certain
network-optimization concepts. We review and exemplify these developments, as
well as offer an outlook for possible future research foci. The latter include
design and uses of non-Boolean network elements, e.g., filters, as well as
other developments motivated by potential novel sensor and biotechnology
applications.
