Cln5 represents a new type of cysteine-based S-depalmitoylase linked to neurodegeneration

Genetic CLN5 variants are associated with childhood neurodegeneration and Alzheimer’s disease; however, the molecular function of ceroid lipofuscinosis neuronal protein 5 (Cln5) is unknown. We solved the Cln5 crystal structure and identified a region homologous to the catalytic domain of members of the N1pC/P60 superfamily of papain-like enzymes. However, we observed no protease activity for Cln5; and instead, we discovered that Cln5 and structurally related PPPDE1 and PPPDE2 have efficient cysteine palmitoyl thioesterase (S-depalmitoylation) activity using fluorescent substrates. Mutational analysis revealed that the predicted catalytic residues histidine-166 and cysteine-280 are critical for Cln5 thioesterase activity, uncovering a new cysteine-based catalytic mechanism for S-depalmitoylation enzymes. Last, we found that Cln5-deficient neuronal progenitor cells showed reduced thioesterase activity, confirming live cell function of Cln5 in setting S-depalmitoylation levels. Our results provide new insight into the function of Cln5, emphasize the importance of S-depalmitoylation in neuronal homeostasis, and disclose a new, unexpected enzymatic function for the N1pC/P60 superfamily of proteins

Reagent for Introducing Base-Stabilized Phosphorus Atoms into Organic and Inorganic Compounds

The cyclic alkyl­(amino) carbene (cAAC) stabilized monoanionic phosphorus atom in the form of lithium phosphinidene [cAACPLi­(THF)₂]₂ (<b>1</b>) has been isolated as a molecular species and characterized by single crystal X-ray structure analysis. Furthermore, the structure and bonding of compound <b>1</b> has been investigated by theoretical methods. The utilization of the lithium phosphinidene as a phosphorus transfer reagent for a wide range of organic and inorganic substrates has been investigated. Herein, we report on the preparation of fascinating compounds containing P–C, P–Si, P–Ge, and P–P bonds using a single step with a base-stabilized phosphorus atom

Comparison of Two Phosphinidenes Binding to Silicon(IV)dichloride as well as to Silylene

The cyclic alkyl­(amino) carbene (cAAC) anchored silylene with two phosphinidenes was isolated as (cAAC)­Si­{P­(cAAC)}₂ (<b>3</b>) at room temperature, which was synthesized from the reduction of (Cl₂)­Si­{P­(cAAC)}₂ (<b>2</b>) using 2 equiv of KC₈. Compound <b>2</b> resulted from the reaction of 2 equiv of (cAAC)­PK (<b>1</b>) with 1 equiv of SiCl₄. Compounds <b>2</b> and <b>3</b> are the first examples where two terminal phosphinidenes are binding each to a silicon center characterized by single crystal X-ray structural analysis. Furthermore, the structure and bonding of compounds <b>2</b> and <b>3</b> have been investigated by theoretical methods for comparison

Comparison of Two Phosphinidenes Binding to Silicon(IV)dichloride as well as to Silylene

The cyclic alkyl­(amino) carbene (cAAC) anchored silylene with two phosphinidenes was isolated as (cAAC)­Si­{P­(cAAC)}₂ (<b>3</b>) at room temperature, which was synthesized from the reduction of (Cl₂)­Si­{P­(cAAC)}₂ (<b>2</b>) using 2 equiv of KC₈. Compound <b>2</b> resulted from the reaction of 2 equiv of (cAAC)­PK (<b>1</b>) with 1 equiv of SiCl₄. Compounds <b>2</b> and <b>3</b> are the first examples where two terminal phosphinidenes are binding each to a silicon center characterized by single crystal X-ray structural analysis. Furthermore, the structure and bonding of compounds <b>2</b> and <b>3</b> have been investigated by theoretical methods for comparison

Comparison of Two Phosphinidenes Binding to Silicon(IV)dichloride as well as to Silylene

The cyclic alkyl­(amino) carbene (cAAC) anchored silylene with two phosphinidenes was isolated as (cAAC)­Si­{P­(cAAC)}₂ (<b>3</b>) at room temperature, which was synthesized from the reduction of (Cl₂)­Si­{P­(cAAC)}₂ (<b>2</b>) using 2 equiv of KC₈. Compound <b>2</b> resulted from the reaction of 2 equiv of (cAAC)­PK (<b>1</b>) with 1 equiv of SiCl₄. Compounds <b>2</b> and <b>3</b> are the first examples where two terminal phosphinidenes are binding each to a silicon center characterized by single crystal X-ray structural analysis. Furthermore, the structure and bonding of compounds <b>2</b> and <b>3</b> have been investigated by theoretical methods for comparison

Cln5 represents a new type of cysteine-based S-depalmitoylase linked to neurodegeneration

Genetic CLN5 variants are associated with childhood neurodegeneration and Alzheimer’s disease; however, the molecular function of ceroid lipofuscinosis neuronal protein 5 (Cln5) is unknown. We solved the Cln5 crystal structure and identified a region homologous to the catalytic domain of members of the N1pC/P60 superfamily of papain-like enzymes. However, we observed no protease activity for Cln5; and instead, we discovered that Cln5 and structurally related PPPDE1 and PPPDE2 have efficient cysteine palmitoyl thioesterase (S-depalmitoylation) activity using fluorescent substrates. Mutational analysis revealed that the predicted catalytic residues histidine-166 and cysteine-280 are critical for Cln5 thioesterase activity, uncovering a new cysteine-based catalytic mechanism for S-depalmitoylation enzymes. Last, we found that Cln5-deficient neuronal progenitor cells showed reduced thioesterase activity, confirming live cell function of Cln5 in setting S-depalmitoylation levels. Our results provide new insight into the function of Cln5, emphasize the importance of S-depalmitoylation in neuronal homeostasis, and disclose a new, unexpected enzymatic function for the N1pC/P60 superfamily of proteins

Organosilicon Radicals with Si–H and Si–Me Bonds from Commodity Precursors

The cyclic alkyl­(amino) carbene (cAAC) stabilized biradicals of composition (cAAC)₂SiH₂ (<b>1</b>), (cAAC)­SiMe₂-SiMe₂(cAAC) (<b>2</b>), and (cAAC)­SiMeCl-SiMeCl­(cAAC) (<b>3</b>) have been isolated as molecular species. All the compounds are stable at room temperature for more than 6 months under inert conditions in the solid state. All radical species were fully characterized by single-crystal X-ray structure analysis and EPR spectroscopy. Furthermore, the structure and bonding of compounds <b>1</b>–<b>3</b> have been investigated by theoretical methods. Compound <b>1</b> contains the SiH₂ moiety and this is the first instance, where we have isolated <b>1</b> without an acceptor molecule