OpgH-associated periplasmic glucan synthesis and processing

OpgH membrane glucosyltransferases support synthesis of beta-glucan backbones in characterized OpgGH-dependent systems. The required native chemical contribution of OpgG remains unresolved. Particular realizations additionally need OpgI or a compatible ACP-dependent membrane system. Periplasmic processing includes E. coli OpgD hydrolysis and Xanthomonas OpgD alpha-1,6 cyclization, which are distinct reactions within the same protein subfamily. Caulobacter OpgH provides a comparative homolog whose native product chemistry remains unresolved.

The required H/G pair describes the OpgGH-associated backbone mechanism, not a sufficient two-gene recipe for a native final product. OpgI and ACP are optional at the generic node but obligatory in their documented conditional systems. Native endpoint checks must enforce those conditions and compatible same-organism partners. The family classifier cannot distinguish SF3 hydrolysis from cyclization, nor does SF5 identify an experimentally proven OPG product in Caulobacter. The separate source-scoped capacity evaluation must enforce actual activity evidence. The Caulobacter comparator cannot satisfy a native OpgGH-product endpoint. Rhodobacter 2.4.1 gene perturbations and WS8 product NMR are distinct experiments. Cyclic products do not imply the Ndv/Chv/Cgs route, which is outside this OpgH-associated mechanism. The module does not equate failed product detection with absence, infer OpgH-alone sufficiency, assign OpgG branching, or make OpgH/FtsZ moonlighting a synthesis requirement. All eleven representative gene reviews are complete. The scoped evaluator distinguishes native-process evidence, supplied-substrate chemistry and qualified inference; it does not infer arbitrary proteome capacity from family labels.